diff --git a/assistant-say-number/functions/.eslintrc.json b/assistant-say-number/functions/.eslintrc.json
new file mode 100644
index 0000000000..eb4c93169b
--- /dev/null
+++ b/assistant-say-number/functions/.eslintrc.json
@@ -0,0 +1,125 @@
+{
+  "parserOptions": {
+    // Required for certain syntax usages
+    "ecmaVersion": 6
+  },
+  "plugins": [
+    "promise"
+  ],
+  "extends": "eslint:recommended",
+  "rules": {
+    // Removed rule "disallow the use of console" from recommended eslint rules
+    "no-console": "off",
+
+    // Removed rule "disallow multiple spaces in regular expressions" from recommended eslint rules
+    "no-regex-spaces": "off",
+
+    // Removed rule "disallow the use of debugger" from recommended eslint rules
+    "no-debugger": "off",
+
+    // Removed rule "disallow unused variables" from recommended eslint rules
+    "no-unused-vars": "off",
+
+    // Removed rule "disallow mixed spaces and tabs for indentation" from recommended eslint rules
+    "no-mixed-spaces-and-tabs": "off",
+
+    // Removed rule "disallow the use of undeclared variables unless mentioned in /*global */ comments" from recommended eslint rules
+    "no-undef": "off",
+
+    // Warn against template literal placeholder syntax in regular strings
+    "no-template-curly-in-string": 1,
+
+    // Warn if return statements do not either always or never specify values
+    "consistent-return": 1,
+
+    // Warn if no return statements in callbacks of array methods
+    "array-callback-return": 1,
+
+    // Requre the use of === and !==
+    "eqeqeq": 2,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    // Disallow the use of alert, confirm, and prompt
+    "no-alert": 2,
+
+    // Disallow the use of arguments.caller or arguments.callee
+    "no-caller": 2,
+
+    // Disallow null comparisons without type-checking operators
+    "no-eq-null": 2,
+
+    // Disallow the use of eval()
+    "no-eval": 2,
+
+    // Warn against extending native types
+    "no-extend-native": 1,
+
+    // Warn against unnecessary calls to .bind()
+    "no-extra-bind": 1,
+
+    // Warn against unnecessary labels    
+    "no-extra-label": 1,
+
+    // Disallow leading or trailing decimal points in numeric literals
+    "no-floating-decimal": 2,
+
+    // Warn against shorthand type conversions
+    "no-implicit-coercion": 1,
+
+    // Warn against function declarations and expressions inside loop statements
+    "no-loop-func": 1,
+
+    // Disallow new operators with the Function object
+    "no-new-func": 2,
+
+    // Warn against new operators with the String, Number, and Boolean objects
+    "no-new-wrappers": 1,
+
+    // Disallow throwing literals as exceptions
+    "no-throw-literal": 2,
+
+    // Require using Error objects as Promise rejection reasons
+    "prefer-promise-reject-errors": 2,
+
+    // Enforce “for” loop update clause moving the counter in the right direction
+    "for-direction": 2,
+
+    // Enforce return statements in getters
+    "getter-return": 2,
+
+    // Disallow await inside of loops
+    "no-await-in-loop": 2,
+
+    // Disallow comparing against -0
+    "no-compare-neg-zero": 2,
+
+    // Warn against catch clause parameters from shadowing variables in the outer scope
+    "no-catch-shadow": 1,
+
+    // Disallow identifiers from shadowing restricted names
+    "no-shadow-restricted-names": 2,
+
+    // Enforce return statements in callbacks of array methods
+    "callback-return": 2,
+
+    // Require error handling in callbacks
+    "handle-callback-err": 2,
+
+    // Warn against string concatenation with __dirname and __filename
+    "no-path-concat": 1,
+
+    // Prefer using arrow functions for callbacks
+    "prefer-arrow-callback": 1,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    //Enforces the use of catch() on un-returned promises
+    "promise/catch-or-return": 2,
+
+    // Warn against nested then() or catch() statements
+    "promise/no-nesting": 1
+  }
+}
diff --git a/assistant-say-number/functions/index.js b/assistant-say-number/functions/index.js
index f086d9d5a6..22836571dc 100644
--- a/assistant-say-number/functions/index.js
+++ b/assistant-say-number/functions/index.js
@@ -30,12 +30,12 @@ exports.sayNumber = functions.https.onRequest((req, res) => {
   const reprompts = [
     'I didn\'t hear a number',
     'If you\'re still there, what\'s the number?',
-    'What is the number?'
+    'What is the number?',
   ];
 
   const actionMap = new Map();
 
-  actionMap.set(assistant.StandardIntents.MAIN, assistant => {
+  actionMap.set(assistant.StandardIntents.MAIN, (assistant) => {
     const inputPrompt = assistant.buildInputPrompt(true, `<speak>
         Hi! <break time="1"/>
         I can read out an ordinal number like <say-as interpret-as="ordinal">123</say-as>.
@@ -45,7 +45,7 @@ exports.sayNumber = functions.https.onRequest((req, res) => {
     assistant.ask(inputPrompt);
   });
 
-  actionMap.set(assistant.StandardIntents.TEXT, assistant => {
+  actionMap.set(assistant.StandardIntents.TEXT, (assistant) => {
     const rawInput = assistant.getRawInput();
     if (rawInput === 'bye') {
       assistant.tell('Goodbye!');
diff --git a/authenticated-json-api/functions/.eslintrc.json b/authenticated-json-api/functions/.eslintrc.json
new file mode 100644
index 0000000000..eb4c93169b
--- /dev/null
+++ b/authenticated-json-api/functions/.eslintrc.json
@@ -0,0 +1,125 @@
+{
+  "parserOptions": {
+    // Required for certain syntax usages
+    "ecmaVersion": 6
+  },
+  "plugins": [
+    "promise"
+  ],
+  "extends": "eslint:recommended",
+  "rules": {
+    // Removed rule "disallow the use of console" from recommended eslint rules
+    "no-console": "off",
+
+    // Removed rule "disallow multiple spaces in regular expressions" from recommended eslint rules
+    "no-regex-spaces": "off",
+
+    // Removed rule "disallow the use of debugger" from recommended eslint rules
+    "no-debugger": "off",
+
+    // Removed rule "disallow unused variables" from recommended eslint rules
+    "no-unused-vars": "off",
+
+    // Removed rule "disallow mixed spaces and tabs for indentation" from recommended eslint rules
+    "no-mixed-spaces-and-tabs": "off",
+
+    // Removed rule "disallow the use of undeclared variables unless mentioned in /*global */ comments" from recommended eslint rules
+    "no-undef": "off",
+
+    // Warn against template literal placeholder syntax in regular strings
+    "no-template-curly-in-string": 1,
+
+    // Warn if return statements do not either always or never specify values
+    "consistent-return": 1,
+
+    // Warn if no return statements in callbacks of array methods
+    "array-callback-return": 1,
+
+    // Requre the use of === and !==
+    "eqeqeq": 2,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    // Disallow the use of alert, confirm, and prompt
+    "no-alert": 2,
+
+    // Disallow the use of arguments.caller or arguments.callee
+    "no-caller": 2,
+
+    // Disallow null comparisons without type-checking operators
+    "no-eq-null": 2,
+
+    // Disallow the use of eval()
+    "no-eval": 2,
+
+    // Warn against extending native types
+    "no-extend-native": 1,
+
+    // Warn against unnecessary calls to .bind()
+    "no-extra-bind": 1,
+
+    // Warn against unnecessary labels    
+    "no-extra-label": 1,
+
+    // Disallow leading or trailing decimal points in numeric literals
+    "no-floating-decimal": 2,
+
+    // Warn against shorthand type conversions
+    "no-implicit-coercion": 1,
+
+    // Warn against function declarations and expressions inside loop statements
+    "no-loop-func": 1,
+
+    // Disallow new operators with the Function object
+    "no-new-func": 2,
+
+    // Warn against new operators with the String, Number, and Boolean objects
+    "no-new-wrappers": 1,
+
+    // Disallow throwing literals as exceptions
+    "no-throw-literal": 2,
+
+    // Require using Error objects as Promise rejection reasons
+    "prefer-promise-reject-errors": 2,
+
+    // Enforce “for” loop update clause moving the counter in the right direction
+    "for-direction": 2,
+
+    // Enforce return statements in getters
+    "getter-return": 2,
+
+    // Disallow await inside of loops
+    "no-await-in-loop": 2,
+
+    // Disallow comparing against -0
+    "no-compare-neg-zero": 2,
+
+    // Warn against catch clause parameters from shadowing variables in the outer scope
+    "no-catch-shadow": 1,
+
+    // Disallow identifiers from shadowing restricted names
+    "no-shadow-restricted-names": 2,
+
+    // Enforce return statements in callbacks of array methods
+    "callback-return": 2,
+
+    // Require error handling in callbacks
+    "handle-callback-err": 2,
+
+    // Warn against string concatenation with __dirname and __filename
+    "no-path-concat": 1,
+
+    // Prefer using arrow functions for callbacks
+    "prefer-arrow-callback": 1,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    //Enforces the use of catch() on un-returned promises
+    "promise/catch-or-return": 2,
+
+    // Warn against nested then() or catch() statements
+    "promise/no-nesting": 1
+  }
+}
diff --git a/authenticated-json-api/functions/index.js b/authenticated-json-api/functions/index.js
index 7e9f4e5bd7..ae943071fd 100644
--- a/authenticated-json-api/functions/index.js
+++ b/authenticated-json-api/functions/index.js
@@ -36,10 +36,10 @@ const authenticate = (req, res, next) => {
     return;
   }
   const idToken = req.headers.authorization.split('Bearer ')[1];
-  admin.auth().verifyIdToken(idToken).then(decodedIdToken => {
+  admin.auth().verifyIdToken(idToken).then((decodedIdToken) => {
     req.user = decodedIdToken;
-    next();
-  }).catch(error => {
+    return next();
+  }).catch(() => {
     res.status(403).send('Unauthorized');
   });
 };
@@ -52,16 +52,16 @@ app.use(authenticate);
 app.post('/messages', (req, res) => {
   const message = req.body.message;
 
-  language.detectSentiment(message).then(results => {
+  language.detectSentiment(message).then((results) => {
     const category = categorizeScore(results[0].score);
     const data = {message: message, sentiment: results, category: category};
     return admin.database().ref(`/users/${req.user.uid}/messages`).push(data);
-  }).then(snapshot => {
+  }).then((snapshot) => {
     return snapshot.ref.once('value');
-  }).then(snapshot => {
+  }).then((snapshot) => {
     const val = snapshot.val();
-    res.status(201).json({message: val.message, category: val.category});
-  }).catch(error => {
+    return res.status(201).json({message: val.message, category: val.category});
+  }).catch((error) => {
     console.log('Error detecting sentiment or saving message', error.message);
     res.sendStatus(500);
   });
@@ -80,14 +80,14 @@ app.get('/messages', (req, res) => {
     return res.status(404).json({errorCode: 404, errorMessage: `category '${category}' not found`});
   }
 
-  query.once('value').then(snapshot => {
-    var messages = [];
-    snapshot.forEach(childSnapshot => {
+  return query.once('value').then((snapshot) => {
+    let messages = [];
+    snapshot.forEach((childSnapshot) => {
       messages.push({key: childSnapshot.key, message: childSnapshot.val().message});
     });
 
     return res.status(200).json(messages);
-  }).catch(error => {
+  }).catch((error) => {
     console.log('Error getting messages', error.message);
     res.sendStatus(500);
   });
@@ -97,15 +97,12 @@ app.get('/messages', (req, res) => {
 // Get details about a message
 app.get('/message/:messageId', (req, res) => {
   const messageId = req.params.messageId;
-  admin.database().ref(`/users/${req.user.uid}/messages/${messageId}`).once('value').then(snapshot => {
-    if (snapshot.val() !== null) {
-      // Cache details in the browser for 5 minutes
-      res.set('Cache-Control', 'private, max-age=300');
-      res.status(200).json(snapshot.val());
-    } else {
-      res.status(404).json({errorCode: 404, errorMessage: `message '${messageId}' not found`});
+  admin.database().ref(`/users/${req.user.uid}/messages/${messageId}`).once('value').then((snapshot) => {
+    if (snapshot.val() === null) {
+        return res.status(404).json({errorCode: 404, errorMessage: `message '${messageId}' not found`});
     }
-  }).catch(error => {
+    return res.set('Cache-Control', 'private, max-age=300');
+  }).catch((error) => {
     console.log('Error getting message details', messageId, error.message);
     res.sendStatus(500);
   });
@@ -115,7 +112,7 @@ app.get('/message/:messageId', (req, res) => {
 exports.api = functions.https.onRequest(app);
 
 // Helper function to categorize a sentiment score as positive, negative, or neutral
-const categorizeScore = score => {
+const categorizeScore = (score) => {
   if (score > 0.25) {
     return 'positive';
   } else if (score < -0.25) {
diff --git a/authorized-https-endpoint/functions/.eslintrc.json b/authorized-https-endpoint/functions/.eslintrc.json
new file mode 100644
index 0000000000..eb4c93169b
--- /dev/null
+++ b/authorized-https-endpoint/functions/.eslintrc.json
@@ -0,0 +1,125 @@
+{
+  "parserOptions": {
+    // Required for certain syntax usages
+    "ecmaVersion": 6
+  },
+  "plugins": [
+    "promise"
+  ],
+  "extends": "eslint:recommended",
+  "rules": {
+    // Removed rule "disallow the use of console" from recommended eslint rules
+    "no-console": "off",
+
+    // Removed rule "disallow multiple spaces in regular expressions" from recommended eslint rules
+    "no-regex-spaces": "off",
+
+    // Removed rule "disallow the use of debugger" from recommended eslint rules
+    "no-debugger": "off",
+
+    // Removed rule "disallow unused variables" from recommended eslint rules
+    "no-unused-vars": "off",
+
+    // Removed rule "disallow mixed spaces and tabs for indentation" from recommended eslint rules
+    "no-mixed-spaces-and-tabs": "off",
+
+    // Removed rule "disallow the use of undeclared variables unless mentioned in /*global */ comments" from recommended eslint rules
+    "no-undef": "off",
+
+    // Warn against template literal placeholder syntax in regular strings
+    "no-template-curly-in-string": 1,
+
+    // Warn if return statements do not either always or never specify values
+    "consistent-return": 1,
+
+    // Warn if no return statements in callbacks of array methods
+    "array-callback-return": 1,
+
+    // Requre the use of === and !==
+    "eqeqeq": 2,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    // Disallow the use of alert, confirm, and prompt
+    "no-alert": 2,
+
+    // Disallow the use of arguments.caller or arguments.callee
+    "no-caller": 2,
+
+    // Disallow null comparisons without type-checking operators
+    "no-eq-null": 2,
+
+    // Disallow the use of eval()
+    "no-eval": 2,
+
+    // Warn against extending native types
+    "no-extend-native": 1,
+
+    // Warn against unnecessary calls to .bind()
+    "no-extra-bind": 1,
+
+    // Warn against unnecessary labels    
+    "no-extra-label": 1,
+
+    // Disallow leading or trailing decimal points in numeric literals
+    "no-floating-decimal": 2,
+
+    // Warn against shorthand type conversions
+    "no-implicit-coercion": 1,
+
+    // Warn against function declarations and expressions inside loop statements
+    "no-loop-func": 1,
+
+    // Disallow new operators with the Function object
+    "no-new-func": 2,
+
+    // Warn against new operators with the String, Number, and Boolean objects
+    "no-new-wrappers": 1,
+
+    // Disallow throwing literals as exceptions
+    "no-throw-literal": 2,
+
+    // Require using Error objects as Promise rejection reasons
+    "prefer-promise-reject-errors": 2,
+
+    // Enforce “for” loop update clause moving the counter in the right direction
+    "for-direction": 2,
+
+    // Enforce return statements in getters
+    "getter-return": 2,
+
+    // Disallow await inside of loops
+    "no-await-in-loop": 2,
+
+    // Disallow comparing against -0
+    "no-compare-neg-zero": 2,
+
+    // Warn against catch clause parameters from shadowing variables in the outer scope
+    "no-catch-shadow": 1,
+
+    // Disallow identifiers from shadowing restricted names
+    "no-shadow-restricted-names": 2,
+
+    // Enforce return statements in callbacks of array methods
+    "callback-return": 2,
+
+    // Require error handling in callbacks
+    "handle-callback-err": 2,
+
+    // Warn against string concatenation with __dirname and __filename
+    "no-path-concat": 1,
+
+    // Prefer using arrow functions for callbacks
+    "prefer-arrow-callback": 1,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    //Enforces the use of catch() on un-returned promises
+    "promise/catch-or-return": 2,
+
+    // Warn against nested then() or catch() statements
+    "promise/no-nesting": 1
+  }
+}
diff --git a/authorized-https-endpoint/functions/index.js b/authorized-https-endpoint/functions/index.js
index e2d0cbaebf..3d7e8f29f1 100644
--- a/authorized-https-endpoint/functions/index.js
+++ b/authorized-https-endpoint/functions/index.js
@@ -50,11 +50,11 @@ const validateFirebaseIdToken = (req, res, next) => {
     // Read the ID Token from cookie.
     idToken = req.cookies.__session;
   }
-  admin.auth().verifyIdToken(idToken).then(decodedIdToken => {
+  admin.auth().verifyIdToken(idToken).then((decodedIdToken) => {
     console.log('ID Token correctly decoded', decodedIdToken);
     req.user = decodedIdToken;
-    next();
-  }).catch(error => {
+    return next();
+  }).catch((error) => {
     console.error('Error while verifying Firebase ID token:', error);
     res.status(403).send('Unauthorized');
   });
diff --git a/bigquery-import/functions/.eslintrc.json b/bigquery-import/functions/.eslintrc.json
new file mode 100644
index 0000000000..eb4c93169b
--- /dev/null
+++ b/bigquery-import/functions/.eslintrc.json
@@ -0,0 +1,125 @@
+{
+  "parserOptions": {
+    // Required for certain syntax usages
+    "ecmaVersion": 6
+  },
+  "plugins": [
+    "promise"
+  ],
+  "extends": "eslint:recommended",
+  "rules": {
+    // Removed rule "disallow the use of console" from recommended eslint rules
+    "no-console": "off",
+
+    // Removed rule "disallow multiple spaces in regular expressions" from recommended eslint rules
+    "no-regex-spaces": "off",
+
+    // Removed rule "disallow the use of debugger" from recommended eslint rules
+    "no-debugger": "off",
+
+    // Removed rule "disallow unused variables" from recommended eslint rules
+    "no-unused-vars": "off",
+
+    // Removed rule "disallow mixed spaces and tabs for indentation" from recommended eslint rules
+    "no-mixed-spaces-and-tabs": "off",
+
+    // Removed rule "disallow the use of undeclared variables unless mentioned in /*global */ comments" from recommended eslint rules
+    "no-undef": "off",
+
+    // Warn against template literal placeholder syntax in regular strings
+    "no-template-curly-in-string": 1,
+
+    // Warn if return statements do not either always or never specify values
+    "consistent-return": 1,
+
+    // Warn if no return statements in callbacks of array methods
+    "array-callback-return": 1,
+
+    // Requre the use of === and !==
+    "eqeqeq": 2,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    // Disallow the use of alert, confirm, and prompt
+    "no-alert": 2,
+
+    // Disallow the use of arguments.caller or arguments.callee
+    "no-caller": 2,
+
+    // Disallow null comparisons without type-checking operators
+    "no-eq-null": 2,
+
+    // Disallow the use of eval()
+    "no-eval": 2,
+
+    // Warn against extending native types
+    "no-extend-native": 1,
+
+    // Warn against unnecessary calls to .bind()
+    "no-extra-bind": 1,
+
+    // Warn against unnecessary labels    
+    "no-extra-label": 1,
+
+    // Disallow leading or trailing decimal points in numeric literals
+    "no-floating-decimal": 2,
+
+    // Warn against shorthand type conversions
+    "no-implicit-coercion": 1,
+
+    // Warn against function declarations and expressions inside loop statements
+    "no-loop-func": 1,
+
+    // Disallow new operators with the Function object
+    "no-new-func": 2,
+
+    // Warn against new operators with the String, Number, and Boolean objects
+    "no-new-wrappers": 1,
+
+    // Disallow throwing literals as exceptions
+    "no-throw-literal": 2,
+
+    // Require using Error objects as Promise rejection reasons
+    "prefer-promise-reject-errors": 2,
+
+    // Enforce “for” loop update clause moving the counter in the right direction
+    "for-direction": 2,
+
+    // Enforce return statements in getters
+    "getter-return": 2,
+
+    // Disallow await inside of loops
+    "no-await-in-loop": 2,
+
+    // Disallow comparing against -0
+    "no-compare-neg-zero": 2,
+
+    // Warn against catch clause parameters from shadowing variables in the outer scope
+    "no-catch-shadow": 1,
+
+    // Disallow identifiers from shadowing restricted names
+    "no-shadow-restricted-names": 2,
+
+    // Enforce return statements in callbacks of array methods
+    "callback-return": 2,
+
+    // Require error handling in callbacks
+    "handle-callback-err": 2,
+
+    // Warn against string concatenation with __dirname and __filename
+    "no-path-concat": 1,
+
+    // Prefer using arrow functions for callbacks
+    "prefer-arrow-callback": 1,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    //Enforces the use of catch() on un-returned promises
+    "promise/catch-or-return": 2,
+
+    // Warn against nested then() or catch() statements
+    "promise/no-nesting": 1
+  }
+}
diff --git a/bigquery-import/functions/index.js b/bigquery-import/functions/index.js
index 846f2eb847..1ebbc44238 100644
--- a/bigquery-import/functions/index.js
+++ b/bigquery-import/functions/index.js
@@ -21,7 +21,7 @@ const bigquery = require('@google-cloud/bigquery')();
 /**
  * Writes all logs from the Realtime Database into bigquery.
  */
-exports.addtobigquery = functions.database.ref('/logs/{logid}').onWrite(event => {
+exports.addtobigquery = functions.database.ref('/logs/{logid}').onWrite((event) => {
   // TODO: Make sure you set the `bigquery.datasetName` Google Cloud environment variable.
   const dataset = bigquery.dataset(functions.config().bigquery.datasetname);
   // TODO: Make sure you set the `bigquery.tableName` Google Cloud environment variable.
@@ -30,6 +30,6 @@ exports.addtobigquery = functions.database.ref('/logs/{logid}').onWrite(event =>
   return table.insert({
     ID: event.data.key,
     MESSAGE: event.data.val().message,
-    NUMBER: event.data.val().number
+    NUMBER: event.data.val().number,
   });
 });
diff --git a/child-count/functions/.eslintrc.json b/child-count/functions/.eslintrc.json
new file mode 100644
index 0000000000..eb4c93169b
--- /dev/null
+++ b/child-count/functions/.eslintrc.json
@@ -0,0 +1,125 @@
+{
+  "parserOptions": {
+    // Required for certain syntax usages
+    "ecmaVersion": 6
+  },
+  "plugins": [
+    "promise"
+  ],
+  "extends": "eslint:recommended",
+  "rules": {
+    // Removed rule "disallow the use of console" from recommended eslint rules
+    "no-console": "off",
+
+    // Removed rule "disallow multiple spaces in regular expressions" from recommended eslint rules
+    "no-regex-spaces": "off",
+
+    // Removed rule "disallow the use of debugger" from recommended eslint rules
+    "no-debugger": "off",
+
+    // Removed rule "disallow unused variables" from recommended eslint rules
+    "no-unused-vars": "off",
+
+    // Removed rule "disallow mixed spaces and tabs for indentation" from recommended eslint rules
+    "no-mixed-spaces-and-tabs": "off",
+
+    // Removed rule "disallow the use of undeclared variables unless mentioned in /*global */ comments" from recommended eslint rules
+    "no-undef": "off",
+
+    // Warn against template literal placeholder syntax in regular strings
+    "no-template-curly-in-string": 1,
+
+    // Warn if return statements do not either always or never specify values
+    "consistent-return": 1,
+
+    // Warn if no return statements in callbacks of array methods
+    "array-callback-return": 1,
+
+    // Requre the use of === and !==
+    "eqeqeq": 2,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    // Disallow the use of alert, confirm, and prompt
+    "no-alert": 2,
+
+    // Disallow the use of arguments.caller or arguments.callee
+    "no-caller": 2,
+
+    // Disallow null comparisons without type-checking operators
+    "no-eq-null": 2,
+
+    // Disallow the use of eval()
+    "no-eval": 2,
+
+    // Warn against extending native types
+    "no-extend-native": 1,
+
+    // Warn against unnecessary calls to .bind()
+    "no-extra-bind": 1,
+
+    // Warn against unnecessary labels    
+    "no-extra-label": 1,
+
+    // Disallow leading or trailing decimal points in numeric literals
+    "no-floating-decimal": 2,
+
+    // Warn against shorthand type conversions
+    "no-implicit-coercion": 1,
+
+    // Warn against function declarations and expressions inside loop statements
+    "no-loop-func": 1,
+
+    // Disallow new operators with the Function object
+    "no-new-func": 2,
+
+    // Warn against new operators with the String, Number, and Boolean objects
+    "no-new-wrappers": 1,
+
+    // Disallow throwing literals as exceptions
+    "no-throw-literal": 2,
+
+    // Require using Error objects as Promise rejection reasons
+    "prefer-promise-reject-errors": 2,
+
+    // Enforce “for” loop update clause moving the counter in the right direction
+    "for-direction": 2,
+
+    // Enforce return statements in getters
+    "getter-return": 2,
+
+    // Disallow await inside of loops
+    "no-await-in-loop": 2,
+
+    // Disallow comparing against -0
+    "no-compare-neg-zero": 2,
+
+    // Warn against catch clause parameters from shadowing variables in the outer scope
+    "no-catch-shadow": 1,
+
+    // Disallow identifiers from shadowing restricted names
+    "no-shadow-restricted-names": 2,
+
+    // Enforce return statements in callbacks of array methods
+    "callback-return": 2,
+
+    // Require error handling in callbacks
+    "handle-callback-err": 2,
+
+    // Warn against string concatenation with __dirname and __filename
+    "no-path-concat": 1,
+
+    // Prefer using arrow functions for callbacks
+    "prefer-arrow-callback": 1,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    //Enforces the use of catch() on un-returned promises
+    "promise/catch-or-return": 2,
+
+    // Warn against nested then() or catch() statements
+    "promise/no-nesting": 1
+  }
+}
diff --git a/child-count/functions/index.js b/child-count/functions/index.js
index 62d96cc4de..718e36eea1 100644
--- a/child-count/functions/index.js
+++ b/child-count/functions/index.js
@@ -20,33 +20,38 @@ const admin = require('firebase-admin');
 admin.initializeApp(functions.config().firebase);
 
 // Keeps track of the length of the 'likes' child list in a separate property.
-exports.countlikechange = functions.database.ref('/posts/{postid}/likes/{likeid}').onWrite(event => {
+exports.countlikechange = functions.database.ref('/posts/{postid}/likes/{likeid}').onWrite((event) => {
   const collectionRef = event.data.ref.parent;
   const countRef = collectionRef.parent.child('likes_count');
 
-  // Return the promise from countRef.transaction() so our function 
+  let increment;
+  if (event.data.exists() && !event.data.previous.exists()) {
+    increment = 1;
+  } else if (!event.data.exists() && event.data.previous.exists()) {
+    increment = -1;
+  } else {
+    return null;
+  }
+
+  // Return the promise from countRef.transaction() so our function
   // waits for this async event to complete before it exits.
-  return countRef.transaction(current => {
-    if (event.data.exists() && !event.data.previous.exists()) {
-      return (current || 0) + 1;
-    }
-    else if (!event.data.exists() && event.data.previous.exists()) {
-      return (current || 0) - 1;
-    }
+  return countRef.transaction((current) => {
+    return (current || 0) + increment;
   }).then(() => {
-    console.log('Counter updated.');
+    return console.log('Counter updated.');
   });
 });
 
 // If the number of likes gets deleted, recount the number of likes
-exports.recountlikes = functions.database.ref('/posts/{postid}/likes_count').onWrite(event => {
+exports.recountlikes = functions.database.ref('/posts/{postid}/likes_count').onWrite((event) => {
   if (!event.data.exists()) {
     const counterRef = event.data.ref;
     const collectionRef = counterRef.parent.child('likes');
-    
-    // Return the promise from counterRef.set() so our function 
+
+    // Return the promise from counterRef.set() so our function
     // waits for this async event to complete before it exits.
     return collectionRef.once('value')
-        .then(messagesData => counterRef.set(messagesData.numChildren()));
+      .then((messagesData) => counterRef.set(messagesData.numChildren()));
   }
+  return null;
 });
diff --git a/convert-images/functions/.eslintrc.json b/convert-images/functions/.eslintrc.json
new file mode 100644
index 0000000000..eb4c93169b
--- /dev/null
+++ b/convert-images/functions/.eslintrc.json
@@ -0,0 +1,125 @@
+{
+  "parserOptions": {
+    // Required for certain syntax usages
+    "ecmaVersion": 6
+  },
+  "plugins": [
+    "promise"
+  ],
+  "extends": "eslint:recommended",
+  "rules": {
+    // Removed rule "disallow the use of console" from recommended eslint rules
+    "no-console": "off",
+
+    // Removed rule "disallow multiple spaces in regular expressions" from recommended eslint rules
+    "no-regex-spaces": "off",
+
+    // Removed rule "disallow the use of debugger" from recommended eslint rules
+    "no-debugger": "off",
+
+    // Removed rule "disallow unused variables" from recommended eslint rules
+    "no-unused-vars": "off",
+
+    // Removed rule "disallow mixed spaces and tabs for indentation" from recommended eslint rules
+    "no-mixed-spaces-and-tabs": "off",
+
+    // Removed rule "disallow the use of undeclared variables unless mentioned in /*global */ comments" from recommended eslint rules
+    "no-undef": "off",
+
+    // Warn against template literal placeholder syntax in regular strings
+    "no-template-curly-in-string": 1,
+
+    // Warn if return statements do not either always or never specify values
+    "consistent-return": 1,
+
+    // Warn if no return statements in callbacks of array methods
+    "array-callback-return": 1,
+
+    // Requre the use of === and !==
+    "eqeqeq": 2,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    // Disallow the use of alert, confirm, and prompt
+    "no-alert": 2,
+
+    // Disallow the use of arguments.caller or arguments.callee
+    "no-caller": 2,
+
+    // Disallow null comparisons without type-checking operators
+    "no-eq-null": 2,
+
+    // Disallow the use of eval()
+    "no-eval": 2,
+
+    // Warn against extending native types
+    "no-extend-native": 1,
+
+    // Warn against unnecessary calls to .bind()
+    "no-extra-bind": 1,
+
+    // Warn against unnecessary labels    
+    "no-extra-label": 1,
+
+    // Disallow leading or trailing decimal points in numeric literals
+    "no-floating-decimal": 2,
+
+    // Warn against shorthand type conversions
+    "no-implicit-coercion": 1,
+
+    // Warn against function declarations and expressions inside loop statements
+    "no-loop-func": 1,
+
+    // Disallow new operators with the Function object
+    "no-new-func": 2,
+
+    // Warn against new operators with the String, Number, and Boolean objects
+    "no-new-wrappers": 1,
+
+    // Disallow throwing literals as exceptions
+    "no-throw-literal": 2,
+
+    // Require using Error objects as Promise rejection reasons
+    "prefer-promise-reject-errors": 2,
+
+    // Enforce “for” loop update clause moving the counter in the right direction
+    "for-direction": 2,
+
+    // Enforce return statements in getters
+    "getter-return": 2,
+
+    // Disallow await inside of loops
+    "no-await-in-loop": 2,
+
+    // Disallow comparing against -0
+    "no-compare-neg-zero": 2,
+
+    // Warn against catch clause parameters from shadowing variables in the outer scope
+    "no-catch-shadow": 1,
+
+    // Disallow identifiers from shadowing restricted names
+    "no-shadow-restricted-names": 2,
+
+    // Enforce return statements in callbacks of array methods
+    "callback-return": 2,
+
+    // Require error handling in callbacks
+    "handle-callback-err": 2,
+
+    // Warn against string concatenation with __dirname and __filename
+    "no-path-concat": 1,
+
+    // Prefer using arrow functions for callbacks
+    "prefer-arrow-callback": 1,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    //Enforces the use of catch() on un-returned promises
+    "promise/catch-or-return": 2,
+
+    // Warn against nested then() or catch() statements
+    "promise/no-nesting": 1
+  }
+}
diff --git a/convert-images/functions/index.js b/convert-images/functions/index.js
index 0e16f9e875..cd0decb24c 100644
--- a/convert-images/functions/index.js
+++ b/convert-images/functions/index.js
@@ -30,7 +30,7 @@ const JPEG_EXTENSION = '.jpg';
  * When an image is uploaded in the Storage bucket it is converted to JPEG automatically using
  * ImageMagick.
  */
-exports.imageToJPG = functions.storage.object().onChange(event => {
+exports.imageToJPG = functions.storage.object().onChange((event) => {
   const object = event.data;
   const filePath = object.name;
   const baseFileName = path.basename(filePath, path.extname(filePath));
@@ -43,19 +43,19 @@ exports.imageToJPG = functions.storage.object().onChange(event => {
   // Exit if this is triggered on a file that is not an image.
   if (!object.contentType.startsWith('image/')) {
     console.log('This is not an image.');
-    return;
+    return null;
   }
 
   // Exit if the image is already a JPEG.
   if (object.contentType.startsWith('image/jpeg')) {
     console.log('Already a JPEG.');
-    return;
+    return null;
   }
 
   // Exit if this is a move or deletion event.
   if (object.resourceState === 'not_exists') {
     console.log('This is a deletion event.');
-    return;
+    return null;
   }
 
   const bucket = gcs.bucket(object.bucket);
@@ -64,8 +64,7 @@ exports.imageToJPG = functions.storage.object().onChange(event => {
     // Download file from bucket.
     return bucket.file(filePath).download({destination: tempLocalFile});
   }).then(() => {
-    console.log('The file has been downloaded to',
-        tempLocalFile);
+    console.log('The file has been downloaded to', tempLocalFile);
     // Convert the image to JPEG using ImageMagick.
     return spawn('convert', [tempLocalFile, tempLocalJPEGFile]);
   }).then(() => {
@@ -77,5 +76,6 @@ exports.imageToJPG = functions.storage.object().onChange(event => {
     // Once the image has been converted delete the local files to free up disk space.
     fs.unlinkSync(tempLocalJPEGFile);
     fs.unlinkSync(tempLocalFile);
+    return;
   });
 });
diff --git a/coupon-on-purchase/functions/.eslintrc.json b/coupon-on-purchase/functions/.eslintrc.json
new file mode 100644
index 0000000000..eb4c93169b
--- /dev/null
+++ b/coupon-on-purchase/functions/.eslintrc.json
@@ -0,0 +1,125 @@
+{
+  "parserOptions": {
+    // Required for certain syntax usages
+    "ecmaVersion": 6
+  },
+  "plugins": [
+    "promise"
+  ],
+  "extends": "eslint:recommended",
+  "rules": {
+    // Removed rule "disallow the use of console" from recommended eslint rules
+    "no-console": "off",
+
+    // Removed rule "disallow multiple spaces in regular expressions" from recommended eslint rules
+    "no-regex-spaces": "off",
+
+    // Removed rule "disallow the use of debugger" from recommended eslint rules
+    "no-debugger": "off",
+
+    // Removed rule "disallow unused variables" from recommended eslint rules
+    "no-unused-vars": "off",
+
+    // Removed rule "disallow mixed spaces and tabs for indentation" from recommended eslint rules
+    "no-mixed-spaces-and-tabs": "off",
+
+    // Removed rule "disallow the use of undeclared variables unless mentioned in /*global */ comments" from recommended eslint rules
+    "no-undef": "off",
+
+    // Warn against template literal placeholder syntax in regular strings
+    "no-template-curly-in-string": 1,
+
+    // Warn if return statements do not either always or never specify values
+    "consistent-return": 1,
+
+    // Warn if no return statements in callbacks of array methods
+    "array-callback-return": 1,
+
+    // Requre the use of === and !==
+    "eqeqeq": 2,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    // Disallow the use of alert, confirm, and prompt
+    "no-alert": 2,
+
+    // Disallow the use of arguments.caller or arguments.callee
+    "no-caller": 2,
+
+    // Disallow null comparisons without type-checking operators
+    "no-eq-null": 2,
+
+    // Disallow the use of eval()
+    "no-eval": 2,
+
+    // Warn against extending native types
+    "no-extend-native": 1,
+
+    // Warn against unnecessary calls to .bind()
+    "no-extra-bind": 1,
+
+    // Warn against unnecessary labels    
+    "no-extra-label": 1,
+
+    // Disallow leading or trailing decimal points in numeric literals
+    "no-floating-decimal": 2,
+
+    // Warn against shorthand type conversions
+    "no-implicit-coercion": 1,
+
+    // Warn against function declarations and expressions inside loop statements
+    "no-loop-func": 1,
+
+    // Disallow new operators with the Function object
+    "no-new-func": 2,
+
+    // Warn against new operators with the String, Number, and Boolean objects
+    "no-new-wrappers": 1,
+
+    // Disallow throwing literals as exceptions
+    "no-throw-literal": 2,
+
+    // Require using Error objects as Promise rejection reasons
+    "prefer-promise-reject-errors": 2,
+
+    // Enforce “for” loop update clause moving the counter in the right direction
+    "for-direction": 2,
+
+    // Enforce return statements in getters
+    "getter-return": 2,
+
+    // Disallow await inside of loops
+    "no-await-in-loop": 2,
+
+    // Disallow comparing against -0
+    "no-compare-neg-zero": 2,
+
+    // Warn against catch clause parameters from shadowing variables in the outer scope
+    "no-catch-shadow": 1,
+
+    // Disallow identifiers from shadowing restricted names
+    "no-shadow-restricted-names": 2,
+
+    // Enforce return statements in callbacks of array methods
+    "callback-return": 2,
+
+    // Require error handling in callbacks
+    "handle-callback-err": 2,
+
+    // Warn against string concatenation with __dirname and __filename
+    "no-path-concat": 1,
+
+    // Prefer using arrow functions for callbacks
+    "prefer-arrow-callback": 1,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    //Enforces the use of catch() on un-returned promises
+    "promise/catch-or-return": 2,
+
+    // Warn against nested then() or catch() statements
+    "promise/no-nesting": 1
+  }
+}
diff --git a/coupon-on-purchase/functions/index.js b/coupon-on-purchase/functions/index.js
index b716a7c9b3..3b5e055cfd 100644
--- a/coupon-on-purchase/functions/index.js
+++ b/coupon-on-purchase/functions/index.js
@@ -24,7 +24,7 @@ admin.initializeApp(functions.config().firebase);
  * After a user has completed a purchase, send them a coupon via FCM valid on their next purchase.
  */
 // [START trigger]
-exports.sendCouponOnPurchase = functions.analytics.event('in_app_purchase').onLog(event => {
+exports.sendCouponOnPurchase = functions.analytics.event('in_app_purchase').onLog((event) => {
 // [END trigger]
   // [START attributes]
   const user = event.data.user;
@@ -49,14 +49,14 @@ exports.sendCouponOnPurchase = functions.analytics.event('in_app_purchase').onLo
  */
 function sendCouponViaFCM(uid, userLanguage) {
   // Fetching all the user's device tokens.
-  return getDeviceTokens(uid).then(tokens => {
+  return getDeviceTokens(uid).then((tokens) => {
     if (tokens.length > 0) {
       // Notification details.
       let payload = {
         notification: {
           title: 'Thanks for your Purchase!',
-          body: 'Get 10% off your next purchase with "COMEBACK10".'
-        }
+          body: 'Get 10% off your next purchase with "COMEBACK10".',
+        },
       };
 
       // Notification in French.
@@ -64,14 +64,15 @@ function sendCouponViaFCM(uid, userLanguage) {
         payload = {
           notification: {
             title: 'Merci pour votre achat!',
-            body: 'Obtenez 10% de réduction sur votre prochain achat avec "COMEBACK10".'
-          }
+            body: 'Obtenez 10% de réduction sur votre prochain achat avec "COMEBACK10".',
+          },
         };
       }
 
       // Send notifications to all tokens.
       return admin.messaging().sendToDevice(tokens, payload);
     }
+    return null;
   });
 }
 
@@ -83,14 +84,14 @@ function sendCouponViaFCM(uid, userLanguage) {
  */
 function sendHighValueCouponViaFCM(uid, userLanguage) {
   // Fetching all the user's device tokens.
-  return getDeviceTokens(uid).then(tokens => {
+  return getDeviceTokens(uid).then((tokens) => {
     if (tokens.length > 0) {
       // Notification details.
       let payload = {
         notification: {
           title: 'Thanks for your Purchase!',
-          body: 'Get 30% off your next purchase with "COMEBACK30".'
-        }
+          body: 'Get 30% off your next purchase with "COMEBACK30".',
+        },
       };
 
       // Notification in French.
@@ -98,14 +99,15 @@ function sendHighValueCouponViaFCM(uid, userLanguage) {
         payload = {
           notification: {
             title: 'Merci pour votre achat!',
-            body: 'Obtenez 30% de réduction sur votre prochain achat avec "COMEBACK30".'
-          }
+            body: 'Obtenez 30% de réduction sur votre prochain achat avec "COMEBACK30".',
+          },
         };
       }
 
       // Send notifications to all tokens.
       return admin.messaging().sendToDevice(tokens, payload);
     }
+    return null;
   });
 }
 
@@ -115,7 +117,7 @@ function sendHighValueCouponViaFCM(uid, userLanguage) {
  * @param {string} uid The UID of the user.
  */
 function getDeviceTokens(uid) {
-  return admin.database().ref(`/users/${uid}/tokens`).once('value').then(snap => {
+  return admin.database().ref(`/users/${uid}/tokens`).once('value').then((snap) => {
     if (snap.exists()) {
       return Object.keys(snap.val());
     }
diff --git a/crashlytics-integration/email-notifier/functions/.eslintrc.json b/crashlytics-integration/email-notifier/functions/.eslintrc.json
new file mode 100644
index 0000000000..eb4c93169b
--- /dev/null
+++ b/crashlytics-integration/email-notifier/functions/.eslintrc.json
@@ -0,0 +1,125 @@
+{
+  "parserOptions": {
+    // Required for certain syntax usages
+    "ecmaVersion": 6
+  },
+  "plugins": [
+    "promise"
+  ],
+  "extends": "eslint:recommended",
+  "rules": {
+    // Removed rule "disallow the use of console" from recommended eslint rules
+    "no-console": "off",
+
+    // Removed rule "disallow multiple spaces in regular expressions" from recommended eslint rules
+    "no-regex-spaces": "off",
+
+    // Removed rule "disallow the use of debugger" from recommended eslint rules
+    "no-debugger": "off",
+
+    // Removed rule "disallow unused variables" from recommended eslint rules
+    "no-unused-vars": "off",
+
+    // Removed rule "disallow mixed spaces and tabs for indentation" from recommended eslint rules
+    "no-mixed-spaces-and-tabs": "off",
+
+    // Removed rule "disallow the use of undeclared variables unless mentioned in /*global */ comments" from recommended eslint rules
+    "no-undef": "off",
+
+    // Warn against template literal placeholder syntax in regular strings
+    "no-template-curly-in-string": 1,
+
+    // Warn if return statements do not either always or never specify values
+    "consistent-return": 1,
+
+    // Warn if no return statements in callbacks of array methods
+    "array-callback-return": 1,
+
+    // Requre the use of === and !==
+    "eqeqeq": 2,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    // Disallow the use of alert, confirm, and prompt
+    "no-alert": 2,
+
+    // Disallow the use of arguments.caller or arguments.callee
+    "no-caller": 2,
+
+    // Disallow null comparisons without type-checking operators
+    "no-eq-null": 2,
+
+    // Disallow the use of eval()
+    "no-eval": 2,
+
+    // Warn against extending native types
+    "no-extend-native": 1,
+
+    // Warn against unnecessary calls to .bind()
+    "no-extra-bind": 1,
+
+    // Warn against unnecessary labels    
+    "no-extra-label": 1,
+
+    // Disallow leading or trailing decimal points in numeric literals
+    "no-floating-decimal": 2,
+
+    // Warn against shorthand type conversions
+    "no-implicit-coercion": 1,
+
+    // Warn against function declarations and expressions inside loop statements
+    "no-loop-func": 1,
+
+    // Disallow new operators with the Function object
+    "no-new-func": 2,
+
+    // Warn against new operators with the String, Number, and Boolean objects
+    "no-new-wrappers": 1,
+
+    // Disallow throwing literals as exceptions
+    "no-throw-literal": 2,
+
+    // Require using Error objects as Promise rejection reasons
+    "prefer-promise-reject-errors": 2,
+
+    // Enforce “for” loop update clause moving the counter in the right direction
+    "for-direction": 2,
+
+    // Enforce return statements in getters
+    "getter-return": 2,
+
+    // Disallow await inside of loops
+    "no-await-in-loop": 2,
+
+    // Disallow comparing against -0
+    "no-compare-neg-zero": 2,
+
+    // Warn against catch clause parameters from shadowing variables in the outer scope
+    "no-catch-shadow": 1,
+
+    // Disallow identifiers from shadowing restricted names
+    "no-shadow-restricted-names": 2,
+
+    // Enforce return statements in callbacks of array methods
+    "callback-return": 2,
+
+    // Require error handling in callbacks
+    "handle-callback-err": 2,
+
+    // Warn against string concatenation with __dirname and __filename
+    "no-path-concat": 1,
+
+    // Prefer using arrow functions for callbacks
+    "prefer-arrow-callback": 1,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    //Enforces the use of catch() on un-returned promises
+    "promise/catch-or-return": 2,
+
+    // Warn against nested then() or catch() statements
+    "promise/no-nesting": 1
+  }
+}
diff --git a/crashlytics-integration/email-notifier/functions/index.js b/crashlytics-integration/email-notifier/functions/index.js
index 68981c9da0..abfb221c54 100644
--- a/crashlytics-integration/email-notifier/functions/index.js
+++ b/crashlytics-integration/email-notifier/functions/index.js
@@ -15,13 +15,13 @@
  */
 'use strict';
 
-const functions = require('firebase-functions'),
-      sendgridMail = require('@sendgrid/mail');
+const functions = require('firebase-functions');
+const sendgridMail = require('@sendgrid/mail');
 
 // Authentication for the SendGrid account
 sendgridMail.setApiKey(functions.config().sendgrid.api_key);
 
-exports.sendOnNewIssue = functions.crashlytics.issue().onNewDetected(event => {
+exports.sendOnNewIssue = functions.crashlytics.issue().onNewDetected((event) => {
   const data = event.data;
 
   const issueId = data.issueId;
@@ -43,17 +43,17 @@ exports.sendOnNewIssue = functions.crashlytics.issue().onNewDetected(event => {
         <p>Version: ${latestAppVersion}</p>
         <p>Issue Id: ${issueId}</p>
         <p>Issue Title: ${issueTitle}</p>
-        <p>Creation Time: ${createTime}</p>`
+        <p>Creation Time: ${createTime}</p>`,
   };
 
   return sendgridMail.send(emailDetails).then(() => {
-    console.log('Successfully sent new issue email');
-  }).catch(error => {
+    return console.log('Successfully sent new issue email');
+  }).catch((error) => {
     console.error(error.toString());
   });
 });
 
-exports.sendOnRegressedIssue = functions.crashlytics.issue().onRegressed(event => {
+exports.sendOnRegressedIssue = functions.crashlytics.issue().onRegressed((event) => {
   const data = event.data;
 
   const issueId = data.issueId;
@@ -77,17 +77,17 @@ exports.sendOnRegressedIssue = functions.crashlytics.issue().onRegressed(event =
         <p>Issue Id: ${issueId}</p>
         <p>Issue Title: ${issueTitle}</p>
         <p>Creation Time: ${createTime}</p>
-        <p>Originally Resolved On: ${new Date(resolvedTime).toString()}</p>`
+        <p>Originally Resolved On: ${new Date(resolvedTime).toString()}</p>`,
   };
 
   return sendgridMail.send(emailDetails).then(() => {
-    console.log('Successfully sent regressed issue email');
-  }).catch(error => {
+    return console.log('Successfully sent regressed issue email');
+  }).catch((error) => {
     console.error(error.toString());
   });
 });
 
-exports.sendOnVelocityAlert = functions.crashlytics.issue().onVelocityAlert(event => {
+exports.sendOnVelocityAlert = functions.crashlytics.issue().onVelocityAlert((event) => {
   const data = event.data;
 
   const issueId = data.issueId;
@@ -113,12 +113,12 @@ exports.sendOnVelocityAlert = functions.crashlytics.issue().onVelocityAlert(even
         <p>Issue Id: ${issueId}</p>
         <p>Issue Title: ${issueTitle}</p>
         <p>Creation Time: ${createTime}</p>
-        <p># of Total Crashes: ${crashes.toString()}</p>`
+        <p># of Total Crashes: ${crashes.toString()}</p>`,
   };
-  
+
   return sendgridMail.send(emailDetails).then(() => {
-    console.log('Successfully sent velocity alert email');
-  }).catch(error => {
+    return console.log('Successfully sent velocity alert email');
+  }).catch((error) => {
     console.error(error.toString());
   });
 });
diff --git a/crashlytics-integration/jira-issue/functions/.eslintrc.json b/crashlytics-integration/jira-issue/functions/.eslintrc.json
new file mode 100644
index 0000000000..eb4c93169b
--- /dev/null
+++ b/crashlytics-integration/jira-issue/functions/.eslintrc.json
@@ -0,0 +1,125 @@
+{
+  "parserOptions": {
+    // Required for certain syntax usages
+    "ecmaVersion": 6
+  },
+  "plugins": [
+    "promise"
+  ],
+  "extends": "eslint:recommended",
+  "rules": {
+    // Removed rule "disallow the use of console" from recommended eslint rules
+    "no-console": "off",
+
+    // Removed rule "disallow multiple spaces in regular expressions" from recommended eslint rules
+    "no-regex-spaces": "off",
+
+    // Removed rule "disallow the use of debugger" from recommended eslint rules
+    "no-debugger": "off",
+
+    // Removed rule "disallow unused variables" from recommended eslint rules
+    "no-unused-vars": "off",
+
+    // Removed rule "disallow mixed spaces and tabs for indentation" from recommended eslint rules
+    "no-mixed-spaces-and-tabs": "off",
+
+    // Removed rule "disallow the use of undeclared variables unless mentioned in /*global */ comments" from recommended eslint rules
+    "no-undef": "off",
+
+    // Warn against template literal placeholder syntax in regular strings
+    "no-template-curly-in-string": 1,
+
+    // Warn if return statements do not either always or never specify values
+    "consistent-return": 1,
+
+    // Warn if no return statements in callbacks of array methods
+    "array-callback-return": 1,
+
+    // Requre the use of === and !==
+    "eqeqeq": 2,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    // Disallow the use of alert, confirm, and prompt
+    "no-alert": 2,
+
+    // Disallow the use of arguments.caller or arguments.callee
+    "no-caller": 2,
+
+    // Disallow null comparisons without type-checking operators
+    "no-eq-null": 2,
+
+    // Disallow the use of eval()
+    "no-eval": 2,
+
+    // Warn against extending native types
+    "no-extend-native": 1,
+
+    // Warn against unnecessary calls to .bind()
+    "no-extra-bind": 1,
+
+    // Warn against unnecessary labels    
+    "no-extra-label": 1,
+
+    // Disallow leading or trailing decimal points in numeric literals
+    "no-floating-decimal": 2,
+
+    // Warn against shorthand type conversions
+    "no-implicit-coercion": 1,
+
+    // Warn against function declarations and expressions inside loop statements
+    "no-loop-func": 1,
+
+    // Disallow new operators with the Function object
+    "no-new-func": 2,
+
+    // Warn against new operators with the String, Number, and Boolean objects
+    "no-new-wrappers": 1,
+
+    // Disallow throwing literals as exceptions
+    "no-throw-literal": 2,
+
+    // Require using Error objects as Promise rejection reasons
+    "prefer-promise-reject-errors": 2,
+
+    // Enforce “for” loop update clause moving the counter in the right direction
+    "for-direction": 2,
+
+    // Enforce return statements in getters
+    "getter-return": 2,
+
+    // Disallow await inside of loops
+    "no-await-in-loop": 2,
+
+    // Disallow comparing against -0
+    "no-compare-neg-zero": 2,
+
+    // Warn against catch clause parameters from shadowing variables in the outer scope
+    "no-catch-shadow": 1,
+
+    // Disallow identifiers from shadowing restricted names
+    "no-shadow-restricted-names": 2,
+
+    // Enforce return statements in callbacks of array methods
+    "callback-return": 2,
+
+    // Require error handling in callbacks
+    "handle-callback-err": 2,
+
+    // Warn against string concatenation with __dirname and __filename
+    "no-path-concat": 1,
+
+    // Prefer using arrow functions for callbacks
+    "prefer-arrow-callback": 1,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    //Enforces the use of catch() on un-returned promises
+    "promise/catch-or-return": 2,
+
+    // Warn against nested then() or catch() statements
+    "promise/no-nesting": 1
+  }
+}
diff --git a/crashlytics-integration/jira-issue/functions/index.js b/crashlytics-integration/jira-issue/functions/index.js
index 2d5371f15a..14bee80301 100644
--- a/crashlytics-integration/jira-issue/functions/index.js
+++ b/crashlytics-integration/jira-issue/functions/index.js
@@ -15,11 +15,11 @@
  */
 'use strict';
 
-const functions = require('firebase-functions'),
-      rp = require('request-promise');
+const functions = require('firebase-functions');
+const rp = require('request-promise');
 
 // Helper function that calculates the priority of the issue
-const calculateIssuePriority = eventType => {
+const calculateIssuePriority = (eventType) => {
   // Run custom logic that can determine the priority or severity of this issue
   // For example, you can parse the stack trace to determine which part of your app
   // is causing the crash and assign priorities based on that
@@ -44,9 +44,9 @@ const calculateIssuePriority = eventType => {
 
 // Helper function that parses the Jira project url and returns an object
 // of the url fragments
-const parseUrl = url => {
+const parseUrl = (url) => {
   // input url format: https://yourdomain.atlassian.net/projects/XX
-  const matches = url.match(/(https?:\/\/)(.+?)(\/.+)?\/(projects|browse)\/([\w\-]+)/);
+  const matches = url.match(/(https?:\/\/)(.+?)(\/.+)?\/(projects|browse)\/([\w-]+)/);
   if (matches && matches.length === 6) {
     return {protocol: matches[1], domain: matches[2], contextPath: matches[3] || '', projectKey: matches[5]};
   } else {
@@ -61,8 +61,8 @@ const createJiraIssue = (summary, description, priority) => {
   const pass = functions.config().jira.pass;
   const issue_type = functions.config().jira.issue_type;
   const component_id = functions.config().jira.component_id;
-  
-  const { protocol, domain, contextPath, projectKey} = parseUrl(project_url);
+
+  const {protocol, domain, contextPath, projectKey} = parseUrl(project_url);
   const baseUrl = [protocol, domain, contextPath].join('');
   const url = `${baseUrl}/rest/api/2/issue`;
 
@@ -71,16 +71,16 @@ const createJiraIssue = (summary, description, priority) => {
   const newIssue = {
     fields: {
       components: [{id: component_id || '10000'}],
-      project: {key: projectKey },
+      project: {key: projectKey},
       summary,
       description,
       issuetype: {
-        name: issue_type || 'Bug'
+        name: issue_type || 'Bug',
       },
       priority: {
         id: priority.toString(),
-      }
-    }
+      },
+    },
   };
 
   // Uses Basic Authentication
@@ -89,16 +89,16 @@ const createJiraIssue = (summary, description, priority) => {
   return rp({
     auth: {
       'user': user,
-      'pass': pass
+      'pass': pass,
     },
     method: 'POST',
     uri: url,
     body: newIssue,
-    json: true
+    json: true,
   });
 };
 
-exports.createNewIssue = functions.crashlytics.issue().onNewDetected(event => {
+exports.createNewIssue = functions.crashlytics.issue().onNewDetected((event) => {
   const data = event.data;
 
   const issueId = data.issueId;
@@ -113,11 +113,11 @@ exports.createNewIssue = functions.crashlytics.issue().onNewDetected(event => {
       `version ${latestAppVersion}`;
   const priority = calculateIssuePriority();
   return createJiraIssue(summary, description, priority).then(() => {
-    console.log(`Created issue ${issueId} in Jira successfully`);
+    return console.log(`Created issue ${issueId} in Jira successfully`);
   });
 });
 
-exports.createRegressedIssue = functions.crashlytics.issue().onRegressed(event => {
+exports.createRegressedIssue = functions.crashlytics.issue().onRegressed((event) => {
   const data = event.data;
 
   const issueId = data.issueId;
@@ -134,11 +134,11 @@ exports.createRegressedIssue = functions.crashlytics.issue().onRegressed(event =
       `${new Date(resolvedTime).toString()}`;
   const priority = calculateIssuePriority('regressed');
   return createJiraIssue(summary, description, priority).then(() => {
-    console.log(`Created issue ${issueId} in Jira successfully`);
+    return console.log(`Created issue ${issueId} in Jira successfully`);
   });
 });
 
-exports.createVelocityAlert = functions.crashlytics.issue().onVelocityAlert(event => {
+exports.createVelocityAlert = functions.crashlytics.issue().onVelocityAlert((event) => {
   const data = event.data;
 
   const issueId = data.issueId;
@@ -155,6 +155,6 @@ exports.createVelocityAlert = functions.crashlytics.issue().onVelocityAlert(even
       `${parseFloat(crashPercentage).toFixed(2)}% of all sessions to crash.`;
   const priority = calculateIssuePriority('velocityAlert');
   return createJiraIssue(summary, description, priority).then(() => {
-    console.log(`Created issue ${issueId} in Jira successfully`);
+    return console.log(`Created issue ${issueId} in Jira successfully`);
   });
 });
diff --git a/crashlytics-integration/slack-notifier/functions/.eslintrc.json b/crashlytics-integration/slack-notifier/functions/.eslintrc.json
new file mode 100644
index 0000000000..eb4c93169b
--- /dev/null
+++ b/crashlytics-integration/slack-notifier/functions/.eslintrc.json
@@ -0,0 +1,125 @@
+{
+  "parserOptions": {
+    // Required for certain syntax usages
+    "ecmaVersion": 6
+  },
+  "plugins": [
+    "promise"
+  ],
+  "extends": "eslint:recommended",
+  "rules": {
+    // Removed rule "disallow the use of console" from recommended eslint rules
+    "no-console": "off",
+
+    // Removed rule "disallow multiple spaces in regular expressions" from recommended eslint rules
+    "no-regex-spaces": "off",
+
+    // Removed rule "disallow the use of debugger" from recommended eslint rules
+    "no-debugger": "off",
+
+    // Removed rule "disallow unused variables" from recommended eslint rules
+    "no-unused-vars": "off",
+
+    // Removed rule "disallow mixed spaces and tabs for indentation" from recommended eslint rules
+    "no-mixed-spaces-and-tabs": "off",
+
+    // Removed rule "disallow the use of undeclared variables unless mentioned in /*global */ comments" from recommended eslint rules
+    "no-undef": "off",
+
+    // Warn against template literal placeholder syntax in regular strings
+    "no-template-curly-in-string": 1,
+
+    // Warn if return statements do not either always or never specify values
+    "consistent-return": 1,
+
+    // Warn if no return statements in callbacks of array methods
+    "array-callback-return": 1,
+
+    // Requre the use of === and !==
+    "eqeqeq": 2,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    // Disallow the use of alert, confirm, and prompt
+    "no-alert": 2,
+
+    // Disallow the use of arguments.caller or arguments.callee
+    "no-caller": 2,
+
+    // Disallow null comparisons without type-checking operators
+    "no-eq-null": 2,
+
+    // Disallow the use of eval()
+    "no-eval": 2,
+
+    // Warn against extending native types
+    "no-extend-native": 1,
+
+    // Warn against unnecessary calls to .bind()
+    "no-extra-bind": 1,
+
+    // Warn against unnecessary labels    
+    "no-extra-label": 1,
+
+    // Disallow leading or trailing decimal points in numeric literals
+    "no-floating-decimal": 2,
+
+    // Warn against shorthand type conversions
+    "no-implicit-coercion": 1,
+
+    // Warn against function declarations and expressions inside loop statements
+    "no-loop-func": 1,
+
+    // Disallow new operators with the Function object
+    "no-new-func": 2,
+
+    // Warn against new operators with the String, Number, and Boolean objects
+    "no-new-wrappers": 1,
+
+    // Disallow throwing literals as exceptions
+    "no-throw-literal": 2,
+
+    // Require using Error objects as Promise rejection reasons
+    "prefer-promise-reject-errors": 2,
+
+    // Enforce “for” loop update clause moving the counter in the right direction
+    "for-direction": 2,
+
+    // Enforce return statements in getters
+    "getter-return": 2,
+
+    // Disallow await inside of loops
+    "no-await-in-loop": 2,
+
+    // Disallow comparing against -0
+    "no-compare-neg-zero": 2,
+
+    // Warn against catch clause parameters from shadowing variables in the outer scope
+    "no-catch-shadow": 1,
+
+    // Disallow identifiers from shadowing restricted names
+    "no-shadow-restricted-names": 2,
+
+    // Enforce return statements in callbacks of array methods
+    "callback-return": 2,
+
+    // Require error handling in callbacks
+    "handle-callback-err": 2,
+
+    // Warn against string concatenation with __dirname and __filename
+    "no-path-concat": 1,
+
+    // Prefer using arrow functions for callbacks
+    "prefer-arrow-callback": 1,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    //Enforces the use of catch() on un-returned promises
+    "promise/catch-or-return": 2,
+
+    // Warn against nested then() or catch() statements
+    "promise/no-nesting": 1
+  }
+}
diff --git a/crashlytics-integration/slack-notifier/functions/index.js b/crashlytics-integration/slack-notifier/functions/index.js
index a09460ee81..21763d4be6 100644
--- a/crashlytics-integration/slack-notifier/functions/index.js
+++ b/crashlytics-integration/slack-notifier/functions/index.js
@@ -15,11 +15,11 @@
  */
 'use strict';
 
-const functions = require('firebase-functions'),
-      rp = require('request-promise');
+const functions = require('firebase-functions');
+const rp = require('request-promise');
 
 // Helper function that posts to Slack about the new issue
-const notifySlack = slackMessage => {
+const notifySlack = (slackMessage) => {
   // See https://api.slack.com/docs/message-formatting on how
   // to customize the message payload
   return rp({
@@ -28,11 +28,11 @@ const notifySlack = slackMessage => {
     body: {
       text: slackMessage,
     },
-    json: true
+    json: true,
   });
 };
 
-exports.postOnNewIssue = functions.crashlytics.issue().onNewDetected(event => {
+exports.postOnNewIssue = functions.crashlytics.issue().onNewDetected((event) => {
   const data = event.data;
 
   const issueId = data.issueId;
@@ -45,11 +45,11 @@ exports.postOnNewIssue = functions.crashlytics.issue().onNewDetected(event => {
       `in ${appName}, version ${latestAppVersion} on ${appPlatform}`;
 
   return notifySlack(slackMessage).then(() => {
-    console.log(`Posted new issue ${issueId} successfully to Slack`);
+    return console.log(`Posted new issue ${issueId} successfully to Slack`);
   });
 });
 
-exports.postOnRegressedIssue = functions.crashlytics.issue().onRegressed(event => {
+exports.postOnRegressedIssue = functions.crashlytics.issue().onRegressed((event) => {
   const data = event.data;
 
   const issueId = data.issueId;
@@ -64,11 +64,11 @@ exports.postOnRegressedIssue = functions.crashlytics.issue().onRegressed(event =
       `resolved at ${new Date(resolvedTime).toString()}`;
 
   return notifySlack(slackMessage).then(() => {
-    console.log(`Posted regressed issue ${issueId} successfully to Slack`);
+    return console.log(`Posted regressed issue ${issueId} successfully to Slack`);
   });
 });
 
-exports.postOnVelocityAlert = functions.crashlytics.issue().onVelocityAlert(event => {
+exports.postOnVelocityAlert = functions.crashlytics.issue().onVelocityAlert((event) => {
   const data = event.data;
 
   const issueId = data.issueId;
@@ -81,7 +81,7 @@ exports.postOnVelocityAlert = functions.crashlytics.issue().onVelocityAlert(even
   const slackMessage = `<!here|here> There is an issue ${issueTitle} (${issueId}) ` +
       `in ${appName}, version ${latestAppVersion} on ${appPlatform} that is causing ` +
       `${parseFloat(crashPercentage).toFixed(2)}% of all sessions to crash.`;
-      
+
   return notifySlack(slackMessage)/then(() => {
     console.log(`Posted velocity alert ${issueId} successfully to Slack`);
   });
diff --git a/delete-old-child-nodes/functions/.eslintrc.json b/delete-old-child-nodes/functions/.eslintrc.json
new file mode 100644
index 0000000000..eb4c93169b
--- /dev/null
+++ b/delete-old-child-nodes/functions/.eslintrc.json
@@ -0,0 +1,125 @@
+{
+  "parserOptions": {
+    // Required for certain syntax usages
+    "ecmaVersion": 6
+  },
+  "plugins": [
+    "promise"
+  ],
+  "extends": "eslint:recommended",
+  "rules": {
+    // Removed rule "disallow the use of console" from recommended eslint rules
+    "no-console": "off",
+
+    // Removed rule "disallow multiple spaces in regular expressions" from recommended eslint rules
+    "no-regex-spaces": "off",
+
+    // Removed rule "disallow the use of debugger" from recommended eslint rules
+    "no-debugger": "off",
+
+    // Removed rule "disallow unused variables" from recommended eslint rules
+    "no-unused-vars": "off",
+
+    // Removed rule "disallow mixed spaces and tabs for indentation" from recommended eslint rules
+    "no-mixed-spaces-and-tabs": "off",
+
+    // Removed rule "disallow the use of undeclared variables unless mentioned in /*global */ comments" from recommended eslint rules
+    "no-undef": "off",
+
+    // Warn against template literal placeholder syntax in regular strings
+    "no-template-curly-in-string": 1,
+
+    // Warn if return statements do not either always or never specify values
+    "consistent-return": 1,
+
+    // Warn if no return statements in callbacks of array methods
+    "array-callback-return": 1,
+
+    // Requre the use of === and !==
+    "eqeqeq": 2,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    // Disallow the use of alert, confirm, and prompt
+    "no-alert": 2,
+
+    // Disallow the use of arguments.caller or arguments.callee
+    "no-caller": 2,
+
+    // Disallow null comparisons without type-checking operators
+    "no-eq-null": 2,
+
+    // Disallow the use of eval()
+    "no-eval": 2,
+
+    // Warn against extending native types
+    "no-extend-native": 1,
+
+    // Warn against unnecessary calls to .bind()
+    "no-extra-bind": 1,
+
+    // Warn against unnecessary labels    
+    "no-extra-label": 1,
+
+    // Disallow leading or trailing decimal points in numeric literals
+    "no-floating-decimal": 2,
+
+    // Warn against shorthand type conversions
+    "no-implicit-coercion": 1,
+
+    // Warn against function declarations and expressions inside loop statements
+    "no-loop-func": 1,
+
+    // Disallow new operators with the Function object
+    "no-new-func": 2,
+
+    // Warn against new operators with the String, Number, and Boolean objects
+    "no-new-wrappers": 1,
+
+    // Disallow throwing literals as exceptions
+    "no-throw-literal": 2,
+
+    // Require using Error objects as Promise rejection reasons
+    "prefer-promise-reject-errors": 2,
+
+    // Enforce “for” loop update clause moving the counter in the right direction
+    "for-direction": 2,
+
+    // Enforce return statements in getters
+    "getter-return": 2,
+
+    // Disallow await inside of loops
+    "no-await-in-loop": 2,
+
+    // Disallow comparing against -0
+    "no-compare-neg-zero": 2,
+
+    // Warn against catch clause parameters from shadowing variables in the outer scope
+    "no-catch-shadow": 1,
+
+    // Disallow identifiers from shadowing restricted names
+    "no-shadow-restricted-names": 2,
+
+    // Enforce return statements in callbacks of array methods
+    "callback-return": 2,
+
+    // Require error handling in callbacks
+    "handle-callback-err": 2,
+
+    // Warn against string concatenation with __dirname and __filename
+    "no-path-concat": 1,
+
+    // Prefer using arrow functions for callbacks
+    "prefer-arrow-callback": 1,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    //Enforces the use of catch() on un-returned promises
+    "promise/catch-or-return": 2,
+
+    // Warn against nested then() or catch() statements
+    "promise/no-nesting": 1
+  }
+}
diff --git a/delete-old-child-nodes/functions/index.js b/delete-old-child-nodes/functions/index.js
index 9ad19b8eba..a142932aba 100644
--- a/delete-old-child-nodes/functions/index.js
+++ b/delete-old-child-nodes/functions/index.js
@@ -27,18 +27,18 @@ const CUT_OFF_TIME = 2 * 60 * 60 * 1000; // 2 Hours in milliseconds.
  * cut-off time. Each child needs to have a `timestamp` attribute.
  */
 exports.deleteOldItems = functions.database.ref('/path/to/items/{pushId}')
-    .onWrite(event => {
+    .onWrite((event) => {
       const ref = event.data.ref.parent; // reference to the items
       const now = Date.now();
       const cutoff = now - CUT_OFF_TIME;
       const oldItemsQuery = ref.orderByChild('timestamp').endAt(cutoff);
-      return oldItemsQuery.once('value').then(snapshot => {
+      return oldItemsQuery.once('value').then((snapshot) => {
         // create a map with all children that need to be removed
         const updates = {};
-        snapshot.forEach(child => {
+        snapshot.forEach((child) => {
           updates[child.key] = null;
         });
         // execute all updates in one go and return the result to end the function
         return ref.update(updates);
       });
-    });
+  });
diff --git a/delete-unused-accounts-cron/functions/.eslintrc.json b/delete-unused-accounts-cron/functions/.eslintrc.json
new file mode 100644
index 0000000000..eb4c93169b
--- /dev/null
+++ b/delete-unused-accounts-cron/functions/.eslintrc.json
@@ -0,0 +1,125 @@
+{
+  "parserOptions": {
+    // Required for certain syntax usages
+    "ecmaVersion": 6
+  },
+  "plugins": [
+    "promise"
+  ],
+  "extends": "eslint:recommended",
+  "rules": {
+    // Removed rule "disallow the use of console" from recommended eslint rules
+    "no-console": "off",
+
+    // Removed rule "disallow multiple spaces in regular expressions" from recommended eslint rules
+    "no-regex-spaces": "off",
+
+    // Removed rule "disallow the use of debugger" from recommended eslint rules
+    "no-debugger": "off",
+
+    // Removed rule "disallow unused variables" from recommended eslint rules
+    "no-unused-vars": "off",
+
+    // Removed rule "disallow mixed spaces and tabs for indentation" from recommended eslint rules
+    "no-mixed-spaces-and-tabs": "off",
+
+    // Removed rule "disallow the use of undeclared variables unless mentioned in /*global */ comments" from recommended eslint rules
+    "no-undef": "off",
+
+    // Warn against template literal placeholder syntax in regular strings
+    "no-template-curly-in-string": 1,
+
+    // Warn if return statements do not either always or never specify values
+    "consistent-return": 1,
+
+    // Warn if no return statements in callbacks of array methods
+    "array-callback-return": 1,
+
+    // Requre the use of === and !==
+    "eqeqeq": 2,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    // Disallow the use of alert, confirm, and prompt
+    "no-alert": 2,
+
+    // Disallow the use of arguments.caller or arguments.callee
+    "no-caller": 2,
+
+    // Disallow null comparisons without type-checking operators
+    "no-eq-null": 2,
+
+    // Disallow the use of eval()
+    "no-eval": 2,
+
+    // Warn against extending native types
+    "no-extend-native": 1,
+
+    // Warn against unnecessary calls to .bind()
+    "no-extra-bind": 1,
+
+    // Warn against unnecessary labels    
+    "no-extra-label": 1,
+
+    // Disallow leading or trailing decimal points in numeric literals
+    "no-floating-decimal": 2,
+
+    // Warn against shorthand type conversions
+    "no-implicit-coercion": 1,
+
+    // Warn against function declarations and expressions inside loop statements
+    "no-loop-func": 1,
+
+    // Disallow new operators with the Function object
+    "no-new-func": 2,
+
+    // Warn against new operators with the String, Number, and Boolean objects
+    "no-new-wrappers": 1,
+
+    // Disallow throwing literals as exceptions
+    "no-throw-literal": 2,
+
+    // Require using Error objects as Promise rejection reasons
+    "prefer-promise-reject-errors": 2,
+
+    // Enforce “for” loop update clause moving the counter in the right direction
+    "for-direction": 2,
+
+    // Enforce return statements in getters
+    "getter-return": 2,
+
+    // Disallow await inside of loops
+    "no-await-in-loop": 2,
+
+    // Disallow comparing against -0
+    "no-compare-neg-zero": 2,
+
+    // Warn against catch clause parameters from shadowing variables in the outer scope
+    "no-catch-shadow": 1,
+
+    // Disallow identifiers from shadowing restricted names
+    "no-shadow-restricted-names": 2,
+
+    // Enforce return statements in callbacks of array methods
+    "callback-return": 2,
+
+    // Require error handling in callbacks
+    "handle-callback-err": 2,
+
+    // Warn against string concatenation with __dirname and __filename
+    "no-path-concat": 1,
+
+    // Prefer using arrow functions for callbacks
+    "prefer-arrow-callback": 1,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    //Enforces the use of catch() on un-returned promises
+    "promise/catch-or-return": 2,
+
+    // Warn against nested then() or catch() statements
+    "promise/no-nesting": 1
+  }
+}
diff --git a/delete-unused-accounts-cron/functions/index.js b/delete-unused-accounts-cron/functions/index.js
index d8c156d531..bdf2208bbe 100644
--- a/delete-unused-accounts-cron/functions/index.js
+++ b/delete-unused-accounts-cron/functions/index.js
@@ -10,7 +10,7 @@
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for t`he specific language governing permissions and
+ * See the License for the specific language governing permissions and
  * limitations under the License.
  */
 'use strict';
@@ -36,63 +36,63 @@ exports.accountcleanup = functions.https.onRequest((req, res) => {
   // Exit if the keys don't match
   if (!secureCompare(key, functions.config().cron.key)) {
     console.log('The key provided in the request does not match the key set in the environment. Check that', key,
-        'matches the cron.key attribute in `firebase env:get`');
+      'matches the cron.key attribute in `firebase env:get`');
     res.status(403).send('Security key does not match. Make sure your "key" URL query parameter matches the ' +
-        'cron.key environment variable.');
-    return;
+      'cron.key environment variable.');
+    return null;
   }
 
   // Fetch all user details.
-  getUsers().then(users => {
+  return getUsers();
+}).then((users) => {
     // Find users that have not signed in in the last 30 days.
     const inactiveUsers = users.filter(
-        user => parseInt(user.lastLoginAt, 10) < Date.now() - 30 * 24 * 60 * 60 * 1000);
+        (user) => parseInt(user.lastLoginAt, 10) < Date.now() - 30 * 24 * 60 * 60 * 1000);
 
     // Use a pool so that we delete maximum `MAX_CONCURRENT` users in parallel.
     const promisePool = new PromisePool(() => {
       if (inactiveUsers.length > 0) {
         const userToDelete = inactiveUsers.pop();
-
         // Delete the inactive user.
-        return admin.auth().deleteUser(userToDelete.localId).then(() => {
-          console.log('Deleted user account', userToDelete.localId, 'because of inactivity');
-        }).catch(error => {
-          console.error('Deletion of inactive user account', userToDelete.localId, 'failed:', error);
-        });
+        return admin.auth().deleteUser(userToDelete.localId);
       }
+      return reject();
     }, MAX_CONCURRENT);
 
-    promisePool.start().then(() => {
-      console.log('User cleanup finished');
-      res.send('User cleanup finished');
-    });
+    return promisePool.start();
+  }).then(() => {
+    return console.log('Deleted user account', userToDelete.localId, 'because of inactivity');
+  }).catch((error) => {
+    console.error('Deletion of inactive user account', userToDelete.localId, 'failed:', error);
+  }).then(() => {
+    console.log('User cleanup finished');
+    return res.send('User cleanup finished');
   });
-});
 
 /**
  * Returns the list of all users with their ID and lastLogin timestamp.
  */
 function getUsers(userIds = [], nextPageToken, accessToken) {
-  return getAccessToken(accessToken).then(accessToken => {
+  return getAccessToken(accessToken).then((accessToken) => {
     const options = {
       method: 'POST',
       uri: 'https://www.googleapis.com/identitytoolkit/v3/relyingparty/downloadAccount?fields=users/localId,users/lastLoginAt,nextPageToken&access_token=' + accessToken,
       body: {
         nextPageToken: nextPageToken,
-        maxResults: 1000
+        maxResults: 1000,
       },
-      json: true
+      json: true,
     };
 
-    return rp(options).then(resp => {
-      if (!resp.users) {
-        return userIds;
-      }
-      if (resp.nextPageToken) {
-        return getUsers(userIds.concat(resp.users), resp.nextPageToken, accessToken);
-      }
-      return userIds.concat(resp.users);
-    });
+    return rp(options);
+  }).then((resp) => {
+    if (!resp.users) {
+      return userIds;
+    }
+    if (resp.nextPageToken) {
+      return getUsers(userIds.concat(resp.users), resp.nextPageToken, accessToken);
+    }
+    return userIds.concat(resp.users);
   });
 }
 
@@ -108,8 +108,8 @@ function getAccessToken(accessToken) {
   const options = {
     uri: 'http://metadata.google.internal/computeMetadata/v1/instance/service-accounts/default/token',
     headers: {'Metadata-Flavor': 'Google'},
-    json: true
+    json: true,
   };
 
-  return rp(options).then(resp => resp.access_token);
+  return rp(options).then((resp) => resp.access_token);
 }
diff --git a/developer-motivator/functions/.eslintrc.json b/developer-motivator/functions/.eslintrc.json
new file mode 100644
index 0000000000..eb4c93169b
--- /dev/null
+++ b/developer-motivator/functions/.eslintrc.json
@@ -0,0 +1,125 @@
+{
+  "parserOptions": {
+    // Required for certain syntax usages
+    "ecmaVersion": 6
+  },
+  "plugins": [
+    "promise"
+  ],
+  "extends": "eslint:recommended",
+  "rules": {
+    // Removed rule "disallow the use of console" from recommended eslint rules
+    "no-console": "off",
+
+    // Removed rule "disallow multiple spaces in regular expressions" from recommended eslint rules
+    "no-regex-spaces": "off",
+
+    // Removed rule "disallow the use of debugger" from recommended eslint rules
+    "no-debugger": "off",
+
+    // Removed rule "disallow unused variables" from recommended eslint rules
+    "no-unused-vars": "off",
+
+    // Removed rule "disallow mixed spaces and tabs for indentation" from recommended eslint rules
+    "no-mixed-spaces-and-tabs": "off",
+
+    // Removed rule "disallow the use of undeclared variables unless mentioned in /*global */ comments" from recommended eslint rules
+    "no-undef": "off",
+
+    // Warn against template literal placeholder syntax in regular strings
+    "no-template-curly-in-string": 1,
+
+    // Warn if return statements do not either always or never specify values
+    "consistent-return": 1,
+
+    // Warn if no return statements in callbacks of array methods
+    "array-callback-return": 1,
+
+    // Requre the use of === and !==
+    "eqeqeq": 2,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    // Disallow the use of alert, confirm, and prompt
+    "no-alert": 2,
+
+    // Disallow the use of arguments.caller or arguments.callee
+    "no-caller": 2,
+
+    // Disallow null comparisons without type-checking operators
+    "no-eq-null": 2,
+
+    // Disallow the use of eval()
+    "no-eval": 2,
+
+    // Warn against extending native types
+    "no-extend-native": 1,
+
+    // Warn against unnecessary calls to .bind()
+    "no-extra-bind": 1,
+
+    // Warn against unnecessary labels    
+    "no-extra-label": 1,
+
+    // Disallow leading or trailing decimal points in numeric literals
+    "no-floating-decimal": 2,
+
+    // Warn against shorthand type conversions
+    "no-implicit-coercion": 1,
+
+    // Warn against function declarations and expressions inside loop statements
+    "no-loop-func": 1,
+
+    // Disallow new operators with the Function object
+    "no-new-func": 2,
+
+    // Warn against new operators with the String, Number, and Boolean objects
+    "no-new-wrappers": 1,
+
+    // Disallow throwing literals as exceptions
+    "no-throw-literal": 2,
+
+    // Require using Error objects as Promise rejection reasons
+    "prefer-promise-reject-errors": 2,
+
+    // Enforce “for” loop update clause moving the counter in the right direction
+    "for-direction": 2,
+
+    // Enforce return statements in getters
+    "getter-return": 2,
+
+    // Disallow await inside of loops
+    "no-await-in-loop": 2,
+
+    // Disallow comparing against -0
+    "no-compare-neg-zero": 2,
+
+    // Warn against catch clause parameters from shadowing variables in the outer scope
+    "no-catch-shadow": 1,
+
+    // Disallow identifiers from shadowing restricted names
+    "no-shadow-restricted-names": 2,
+
+    // Enforce return statements in callbacks of array methods
+    "callback-return": 2,
+
+    // Require error handling in callbacks
+    "handle-callback-err": 2,
+
+    // Warn against string concatenation with __dirname and __filename
+    "no-path-concat": 1,
+
+    // Prefer using arrow functions for callbacks
+    "prefer-arrow-callback": 1,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    //Enforces the use of catch() on un-returned promises
+    "promise/catch-or-return": 2,
+
+    // Warn against nested then() or catch() statements
+    "promise/no-nesting": 1
+  }
+}
diff --git a/developer-motivator/functions/index.js b/developer-motivator/functions/index.js
index 2c2d121bf5..9a8cd510c7 100644
--- a/developer-motivator/functions/index.js
+++ b/developer-motivator/functions/index.js
@@ -26,15 +26,14 @@ const deviceToken = functions.config().dev_motivator.device_token;
  *
  * The device model name, the city and the country of the user are sent in the notification message
  */
-exports.appinstalled = functions.analytics.event('first_open').onLog(event => {
-    const payload = {
-      notification: {
-        title: 'you have a new user \uD83D\uDE43',
-        body: event.data.user.deviceInfo.mobileModelName + ' from ' + event.data.user.geoInfo.city + ', ' + event.data.user.geoInfo.country
-      }
-    };
-
-    admin.messaging().sendToDevice(deviceToken, payload);
+exports.appinstalled = functions.analytics.event('first_open').onLog((event) => {
+  const payload = {
+    notification: {
+      title: 'you have a new user \uD83D\uDE43',
+      body: event.data.user.deviceInfo.mobileModelName + ' from ' + event.data.user.geoInfo.city + ', ' + event.data.user.geoInfo.country,
+    },
+  };
+  admin.messaging().sendToDevice(deviceToken, payload);
 });
 
 /**
@@ -44,14 +43,14 @@ exports.appinstalled = functions.analytics.event('first_open').onLog(event => {
  *
  * The device model name, the city and the country of the user are sent in the notification message
  */
-exports.appremoved = functions.analytics.event('app_remove').onLog(event => {
-    const payload = {
-      notification: {
-        title: 'you lost a user \uD83D\uDE1E',
-        body: event.data.user.deviceInfo.mobileModelName + ' from ' + event.data.user.geoInfo.city + ', ' + event.data.user.geoInfo.country
-      }
-    };
+exports.appremoved = functions.analytics.event('app_remove').onLog((event) => {
+  const payload = {
+    notification: {
+      title: 'you lost a user \uD83D\uDE1E',
+      body: event.data.user.deviceInfo.mobileModelName + ' from ' + event.data.user.geoInfo.city + ', ' + event.data.user.geoInfo.country,
+    },
+  };
 
-    admin.messaging().sendToDevice(deviceToken, payload);
+  admin.messaging().sendToDevice(deviceToken, payload);
 });
 
diff --git a/email-confirmation/functions/.eslintrc.json b/email-confirmation/functions/.eslintrc.json
new file mode 100644
index 0000000000..eb4c93169b
--- /dev/null
+++ b/email-confirmation/functions/.eslintrc.json
@@ -0,0 +1,125 @@
+{
+  "parserOptions": {
+    // Required for certain syntax usages
+    "ecmaVersion": 6
+  },
+  "plugins": [
+    "promise"
+  ],
+  "extends": "eslint:recommended",
+  "rules": {
+    // Removed rule "disallow the use of console" from recommended eslint rules
+    "no-console": "off",
+
+    // Removed rule "disallow multiple spaces in regular expressions" from recommended eslint rules
+    "no-regex-spaces": "off",
+
+    // Removed rule "disallow the use of debugger" from recommended eslint rules
+    "no-debugger": "off",
+
+    // Removed rule "disallow unused variables" from recommended eslint rules
+    "no-unused-vars": "off",
+
+    // Removed rule "disallow mixed spaces and tabs for indentation" from recommended eslint rules
+    "no-mixed-spaces-and-tabs": "off",
+
+    // Removed rule "disallow the use of undeclared variables unless mentioned in /*global */ comments" from recommended eslint rules
+    "no-undef": "off",
+
+    // Warn against template literal placeholder syntax in regular strings
+    "no-template-curly-in-string": 1,
+
+    // Warn if return statements do not either always or never specify values
+    "consistent-return": 1,
+
+    // Warn if no return statements in callbacks of array methods
+    "array-callback-return": 1,
+
+    // Requre the use of === and !==
+    "eqeqeq": 2,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    // Disallow the use of alert, confirm, and prompt
+    "no-alert": 2,
+
+    // Disallow the use of arguments.caller or arguments.callee
+    "no-caller": 2,
+
+    // Disallow null comparisons without type-checking operators
+    "no-eq-null": 2,
+
+    // Disallow the use of eval()
+    "no-eval": 2,
+
+    // Warn against extending native types
+    "no-extend-native": 1,
+
+    // Warn against unnecessary calls to .bind()
+    "no-extra-bind": 1,
+
+    // Warn against unnecessary labels    
+    "no-extra-label": 1,
+
+    // Disallow leading or trailing decimal points in numeric literals
+    "no-floating-decimal": 2,
+
+    // Warn against shorthand type conversions
+    "no-implicit-coercion": 1,
+
+    // Warn against function declarations and expressions inside loop statements
+    "no-loop-func": 1,
+
+    // Disallow new operators with the Function object
+    "no-new-func": 2,
+
+    // Warn against new operators with the String, Number, and Boolean objects
+    "no-new-wrappers": 1,
+
+    // Disallow throwing literals as exceptions
+    "no-throw-literal": 2,
+
+    // Require using Error objects as Promise rejection reasons
+    "prefer-promise-reject-errors": 2,
+
+    // Enforce “for” loop update clause moving the counter in the right direction
+    "for-direction": 2,
+
+    // Enforce return statements in getters
+    "getter-return": 2,
+
+    // Disallow await inside of loops
+    "no-await-in-loop": 2,
+
+    // Disallow comparing against -0
+    "no-compare-neg-zero": 2,
+
+    // Warn against catch clause parameters from shadowing variables in the outer scope
+    "no-catch-shadow": 1,
+
+    // Disallow identifiers from shadowing restricted names
+    "no-shadow-restricted-names": 2,
+
+    // Enforce return statements in callbacks of array methods
+    "callback-return": 2,
+
+    // Require error handling in callbacks
+    "handle-callback-err": 2,
+
+    // Warn against string concatenation with __dirname and __filename
+    "no-path-concat": 1,
+
+    // Prefer using arrow functions for callbacks
+    "prefer-arrow-callback": 1,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    //Enforces the use of catch() on un-returned promises
+    "promise/catch-or-return": 2,
+
+    // Warn against nested then() or catch() statements
+    "promise/no-nesting": 1
+  }
+}
diff --git a/email-confirmation/functions/index.js b/email-confirmation/functions/index.js
index 7d45ca967b..2e96533996 100644
--- a/email-confirmation/functions/index.js
+++ b/email-confirmation/functions/index.js
@@ -26,12 +26,12 @@ const mailTransport = nodemailer.createTransport({
   service: 'gmail',
   auth: {
     user: gmailEmail,
-    pass: gmailPassword
-  }
+    pass: gmailPassword,
+  },
 });
 
 // Sends an email confirmation when a user changes his mailing list subscription.
-exports.sendEmailConfirmation = functions.database.ref('/users/{uid}').onWrite(event => {
+exports.sendEmailConfirmation = functions.database.ref('/users/{uid}').onWrite((event) => {
   const snapshot = event.data;
   const val = snapshot.val();
 
@@ -41,16 +41,16 @@ exports.sendEmailConfirmation = functions.database.ref('/users/{uid}').onWrite(e
 
   const mailOptions = {
     from: '"Spammy Corp." <noreply@firebase.com>',
-    to: val.email
+    to: val.email,
   };
-  
+
   const subscribed = val.subscribedToMailingList;
 
   // Building Email message.
   mailOptions.subject = subscribed ? 'Thanks and Welcome!' : 'Sad to see you go :`(';
   mailOptions.text = subscribed ? 'Thanks you for subscribing to our newsletter. You will receive our next weekly newsletter.' : 'I hereby confirm that I will stop sending you the newsletter.';
-  
+
   return mailTransport.sendMail(mailOptions)
     .then(() => console.log(`New ${subscribed ? '' : 'un'}subscription confirmation email sent to:`, val.email))
-    .catch(error => console.error('There was an error while sending the email:', error));
+    .catch((error) => console.error('There was an error while sending the email:', error));
 });
diff --git a/es2017-transpile/functions/.eslintrc.json b/es2017-transpile/functions/.eslintrc.json
new file mode 100644
index 0000000000..eb4c93169b
--- /dev/null
+++ b/es2017-transpile/functions/.eslintrc.json
@@ -0,0 +1,125 @@
+{
+  "parserOptions": {
+    // Required for certain syntax usages
+    "ecmaVersion": 6
+  },
+  "plugins": [
+    "promise"
+  ],
+  "extends": "eslint:recommended",
+  "rules": {
+    // Removed rule "disallow the use of console" from recommended eslint rules
+    "no-console": "off",
+
+    // Removed rule "disallow multiple spaces in regular expressions" from recommended eslint rules
+    "no-regex-spaces": "off",
+
+    // Removed rule "disallow the use of debugger" from recommended eslint rules
+    "no-debugger": "off",
+
+    // Removed rule "disallow unused variables" from recommended eslint rules
+    "no-unused-vars": "off",
+
+    // Removed rule "disallow mixed spaces and tabs for indentation" from recommended eslint rules
+    "no-mixed-spaces-and-tabs": "off",
+
+    // Removed rule "disallow the use of undeclared variables unless mentioned in /*global */ comments" from recommended eslint rules
+    "no-undef": "off",
+
+    // Warn against template literal placeholder syntax in regular strings
+    "no-template-curly-in-string": 1,
+
+    // Warn if return statements do not either always or never specify values
+    "consistent-return": 1,
+
+    // Warn if no return statements in callbacks of array methods
+    "array-callback-return": 1,
+
+    // Requre the use of === and !==
+    "eqeqeq": 2,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    // Disallow the use of alert, confirm, and prompt
+    "no-alert": 2,
+
+    // Disallow the use of arguments.caller or arguments.callee
+    "no-caller": 2,
+
+    // Disallow null comparisons without type-checking operators
+    "no-eq-null": 2,
+
+    // Disallow the use of eval()
+    "no-eval": 2,
+
+    // Warn against extending native types
+    "no-extend-native": 1,
+
+    // Warn against unnecessary calls to .bind()
+    "no-extra-bind": 1,
+
+    // Warn against unnecessary labels    
+    "no-extra-label": 1,
+
+    // Disallow leading or trailing decimal points in numeric literals
+    "no-floating-decimal": 2,
+
+    // Warn against shorthand type conversions
+    "no-implicit-coercion": 1,
+
+    // Warn against function declarations and expressions inside loop statements
+    "no-loop-func": 1,
+
+    // Disallow new operators with the Function object
+    "no-new-func": 2,
+
+    // Warn against new operators with the String, Number, and Boolean objects
+    "no-new-wrappers": 1,
+
+    // Disallow throwing literals as exceptions
+    "no-throw-literal": 2,
+
+    // Require using Error objects as Promise rejection reasons
+    "prefer-promise-reject-errors": 2,
+
+    // Enforce “for” loop update clause moving the counter in the right direction
+    "for-direction": 2,
+
+    // Enforce return statements in getters
+    "getter-return": 2,
+
+    // Disallow await inside of loops
+    "no-await-in-loop": 2,
+
+    // Disallow comparing against -0
+    "no-compare-neg-zero": 2,
+
+    // Warn against catch clause parameters from shadowing variables in the outer scope
+    "no-catch-shadow": 1,
+
+    // Disallow identifiers from shadowing restricted names
+    "no-shadow-restricted-names": 2,
+
+    // Enforce return statements in callbacks of array methods
+    "callback-return": 2,
+
+    // Require error handling in callbacks
+    "handle-callback-err": 2,
+
+    // Warn against string concatenation with __dirname and __filename
+    "no-path-concat": 1,
+
+    // Prefer using arrow functions for callbacks
+    "prefer-arrow-callback": 1,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    //Enforces the use of catch() on un-returned promises
+    "promise/catch-or-return": 2,
+
+    // Warn against nested then() or catch() statements
+    "promise/no-nesting": 1
+  }
+}
diff --git a/exif-images/functions/.eslintrc.json b/exif-images/functions/.eslintrc.json
new file mode 100644
index 0000000000..eb4c93169b
--- /dev/null
+++ b/exif-images/functions/.eslintrc.json
@@ -0,0 +1,125 @@
+{
+  "parserOptions": {
+    // Required for certain syntax usages
+    "ecmaVersion": 6
+  },
+  "plugins": [
+    "promise"
+  ],
+  "extends": "eslint:recommended",
+  "rules": {
+    // Removed rule "disallow the use of console" from recommended eslint rules
+    "no-console": "off",
+
+    // Removed rule "disallow multiple spaces in regular expressions" from recommended eslint rules
+    "no-regex-spaces": "off",
+
+    // Removed rule "disallow the use of debugger" from recommended eslint rules
+    "no-debugger": "off",
+
+    // Removed rule "disallow unused variables" from recommended eslint rules
+    "no-unused-vars": "off",
+
+    // Removed rule "disallow mixed spaces and tabs for indentation" from recommended eslint rules
+    "no-mixed-spaces-and-tabs": "off",
+
+    // Removed rule "disallow the use of undeclared variables unless mentioned in /*global */ comments" from recommended eslint rules
+    "no-undef": "off",
+
+    // Warn against template literal placeholder syntax in regular strings
+    "no-template-curly-in-string": 1,
+
+    // Warn if return statements do not either always or never specify values
+    "consistent-return": 1,
+
+    // Warn if no return statements in callbacks of array methods
+    "array-callback-return": 1,
+
+    // Requre the use of === and !==
+    "eqeqeq": 2,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    // Disallow the use of alert, confirm, and prompt
+    "no-alert": 2,
+
+    // Disallow the use of arguments.caller or arguments.callee
+    "no-caller": 2,
+
+    // Disallow null comparisons without type-checking operators
+    "no-eq-null": 2,
+
+    // Disallow the use of eval()
+    "no-eval": 2,
+
+    // Warn against extending native types
+    "no-extend-native": 1,
+
+    // Warn against unnecessary calls to .bind()
+    "no-extra-bind": 1,
+
+    // Warn against unnecessary labels    
+    "no-extra-label": 1,
+
+    // Disallow leading or trailing decimal points in numeric literals
+    "no-floating-decimal": 2,
+
+    // Warn against shorthand type conversions
+    "no-implicit-coercion": 1,
+
+    // Warn against function declarations and expressions inside loop statements
+    "no-loop-func": 1,
+
+    // Disallow new operators with the Function object
+    "no-new-func": 2,
+
+    // Warn against new operators with the String, Number, and Boolean objects
+    "no-new-wrappers": 1,
+
+    // Disallow throwing literals as exceptions
+    "no-throw-literal": 2,
+
+    // Require using Error objects as Promise rejection reasons
+    "prefer-promise-reject-errors": 2,
+
+    // Enforce “for” loop update clause moving the counter in the right direction
+    "for-direction": 2,
+
+    // Enforce return statements in getters
+    "getter-return": 2,
+
+    // Disallow await inside of loops
+    "no-await-in-loop": 2,
+
+    // Disallow comparing against -0
+    "no-compare-neg-zero": 2,
+
+    // Warn against catch clause parameters from shadowing variables in the outer scope
+    "no-catch-shadow": 1,
+
+    // Disallow identifiers from shadowing restricted names
+    "no-shadow-restricted-names": 2,
+
+    // Enforce return statements in callbacks of array methods
+    "callback-return": 2,
+
+    // Require error handling in callbacks
+    "handle-callback-err": 2,
+
+    // Warn against string concatenation with __dirname and __filename
+    "no-path-concat": 1,
+
+    // Prefer using arrow functions for callbacks
+    "prefer-arrow-callback": 1,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    //Enforces the use of catch() on un-returned promises
+    "promise/catch-or-return": 2,
+
+    // Warn against nested then() or catch() statements
+    "promise/no-nesting": 1
+  }
+}
diff --git a/exif-images/functions/index.js b/exif-images/functions/index.js
index 86506574f0..9c1580cc45 100644
--- a/exif-images/functions/index.js
+++ b/exif-images/functions/index.js
@@ -30,7 +30,7 @@ const spawn = require('child-process-promise').spawn;
  * When an image is uploaded in the Storage bucket the information and metadata of the image (the
  * output of ImageMagick's `identify -verbose`) is saved in the Realtime Database.
  */
-exports.metadata = functions.storage.object().onChange(event => {
+exports.metadata = functions.storage.object().onChange((event) => {
   const object = event.data;
   const filePath = object.name;
 
@@ -41,31 +41,31 @@ exports.metadata = functions.storage.object().onChange(event => {
   // Exit if this is triggered on a file that is not an image.
   if (!object.contentType.startsWith('image/')) {
     console.log('This is not an image.');
-    return;
+    return null;
   }
 
   // Exit if this is a move or deletion event.
   if (object.resourceState === 'not_exists') {
     console.log('This is a deletion event.');
-    return;
+    return null;
   }
 
   // Download file from bucket.
   const bucket = gcs.bucket(object.bucket);
   return bucket.file(filePath).download({destination: tempLocalFile}).then(() => {
     // Get Metadata from image.
-    return spawn('identify', ['-verbose', tempLocalFile], { capture: [ 'stdout', 'stderr' ]}).then(result => {
-      const metadata = imageMagickOutputToObject(result.stdout);
-      // Save metadata to realtime datastore.
-      return admin.database().ref(makeKeyFirebaseCompatible(filePath)).set(metadata).then(() => {
-        console.log('Wrote to:', filePath, 'data:', metadata);
-      });
-    });
+    return spawn('identify', ['-verbose', tempLocalFile], {capture: ['stdout', 'stderr']});
+  }).then(() => {
+    const metadata = imageMagickOutputToObject(result.stdout);
+    // Save metadata to realtime datastore.
+    return admin.database().ref(makeKeyFirebaseCompatible(filePath)).set(metadata);
+  }).then(() => {
+    return console.log('Wrote to:', filePath, 'data:', metadata);
   }).then(() => {
     // Cleanup temp directory after metadata is extracted
     // Remove the file from temp directory
     fs.unlinkSync(tempLocalFile);
-    console.log('cleanup successful!');
+    return console.log('cleanup successful!');
   });
 });
 
diff --git a/fcm-notifications/functions/.eslintrc.json b/fcm-notifications/functions/.eslintrc.json
new file mode 100644
index 0000000000..eb4c93169b
--- /dev/null
+++ b/fcm-notifications/functions/.eslintrc.json
@@ -0,0 +1,125 @@
+{
+  "parserOptions": {
+    // Required for certain syntax usages
+    "ecmaVersion": 6
+  },
+  "plugins": [
+    "promise"
+  ],
+  "extends": "eslint:recommended",
+  "rules": {
+    // Removed rule "disallow the use of console" from recommended eslint rules
+    "no-console": "off",
+
+    // Removed rule "disallow multiple spaces in regular expressions" from recommended eslint rules
+    "no-regex-spaces": "off",
+
+    // Removed rule "disallow the use of debugger" from recommended eslint rules
+    "no-debugger": "off",
+
+    // Removed rule "disallow unused variables" from recommended eslint rules
+    "no-unused-vars": "off",
+
+    // Removed rule "disallow mixed spaces and tabs for indentation" from recommended eslint rules
+    "no-mixed-spaces-and-tabs": "off",
+
+    // Removed rule "disallow the use of undeclared variables unless mentioned in /*global */ comments" from recommended eslint rules
+    "no-undef": "off",
+
+    // Warn against template literal placeholder syntax in regular strings
+    "no-template-curly-in-string": 1,
+
+    // Warn if return statements do not either always or never specify values
+    "consistent-return": 1,
+
+    // Warn if no return statements in callbacks of array methods
+    "array-callback-return": 1,
+
+    // Requre the use of === and !==
+    "eqeqeq": 2,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    // Disallow the use of alert, confirm, and prompt
+    "no-alert": 2,
+
+    // Disallow the use of arguments.caller or arguments.callee
+    "no-caller": 2,
+
+    // Disallow null comparisons without type-checking operators
+    "no-eq-null": 2,
+
+    // Disallow the use of eval()
+    "no-eval": 2,
+
+    // Warn against extending native types
+    "no-extend-native": 1,
+
+    // Warn against unnecessary calls to .bind()
+    "no-extra-bind": 1,
+
+    // Warn against unnecessary labels    
+    "no-extra-label": 1,
+
+    // Disallow leading or trailing decimal points in numeric literals
+    "no-floating-decimal": 2,
+
+    // Warn against shorthand type conversions
+    "no-implicit-coercion": 1,
+
+    // Warn against function declarations and expressions inside loop statements
+    "no-loop-func": 1,
+
+    // Disallow new operators with the Function object
+    "no-new-func": 2,
+
+    // Warn against new operators with the String, Number, and Boolean objects
+    "no-new-wrappers": 1,
+
+    // Disallow throwing literals as exceptions
+    "no-throw-literal": 2,
+
+    // Require using Error objects as Promise rejection reasons
+    "prefer-promise-reject-errors": 2,
+
+    // Enforce “for” loop update clause moving the counter in the right direction
+    "for-direction": 2,
+
+    // Enforce return statements in getters
+    "getter-return": 2,
+
+    // Disallow await inside of loops
+    "no-await-in-loop": 2,
+
+    // Disallow comparing against -0
+    "no-compare-neg-zero": 2,
+
+    // Warn against catch clause parameters from shadowing variables in the outer scope
+    "no-catch-shadow": 1,
+
+    // Disallow identifiers from shadowing restricted names
+    "no-shadow-restricted-names": 2,
+
+    // Enforce return statements in callbacks of array methods
+    "callback-return": 2,
+
+    // Require error handling in callbacks
+    "handle-callback-err": 2,
+
+    // Warn against string concatenation with __dirname and __filename
+    "no-path-concat": 1,
+
+    // Prefer using arrow functions for callbacks
+    "prefer-arrow-callback": 1,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    //Enforces the use of catch() on un-returned promises
+    "promise/catch-or-return": 2,
+
+    // Warn against nested then() or catch() statements
+    "promise/no-nesting": 1
+  }
+}
diff --git a/fcm-notifications/functions/index.js b/fcm-notifications/functions/index.js
index 205e8be54e..2c234acef2 100644
--- a/fcm-notifications/functions/index.js
+++ b/fcm-notifications/functions/index.js
@@ -25,7 +25,7 @@ admin.initializeApp(functions.config().firebase);
  * Followers add a flag to `/followers/{followedUid}/{followerUid}`.
  * Users save their device notification tokens to `/users/{followedUid}/notificationTokens/{notificationToken}`.
  */
-exports.sendFollowerNotification = functions.database.ref('/followers/{followedUid}/{followerUid}').onWrite(event => {
+exports.sendFollowerNotification = functions.database.ref('/followers/{followedUid}/{followerUid}').onWrite((event) => {
   const followerUid = event.params.followerUid;
   const followedUid = event.params.followedUid;
   // If un-follow we exit the function.
@@ -40,7 +40,7 @@ exports.sendFollowerNotification = functions.database.ref('/followers/{followedU
   // Get the follower profile.
   const getFollowerProfilePromise = admin.auth().getUser(followerUid);
 
-  return Promise.all([getDeviceTokensPromise, getFollowerProfilePromise]).then(results => {
+  return Promise.all([getDeviceTokensPromise, getFollowerProfilePromise]).then((results) => {
     const tokensSnapshot = results[0];
     const follower = results[1];
 
@@ -56,29 +56,28 @@ exports.sendFollowerNotification = functions.database.ref('/followers/{followedU
       notification: {
         title: 'You have a new follower!',
         body: `${follower.displayName} is now following you.`,
-        icon: follower.photoURL
-      }
+        icon: follower.photoURL,
+      },
     };
 
     // Listing all tokens.
     const tokens = Object.keys(tokensSnapshot.val());
 
     // Send notifications to all tokens.
-    return admin.messaging().sendToDevice(tokens, payload).then(response => {
-      // For each message check if there was an error.
-      const tokensToRemove = [];
-      response.results.forEach((result, index) => {
-        const error = result.error;
-        if (error) {
-          console.error('Failure sending notification to', tokens[index], error);
-          // Cleanup the tokens who are not registered anymore.
-          if (error.code === 'messaging/invalid-registration-token' ||
-              error.code === 'messaging/registration-token-not-registered') {
-            tokensToRemove.push(tokensSnapshot.ref.child(tokens[index]).remove());
-          }
+    return admin.messaging().sendToDevice(tokens, payload);
+  }).then((response) => {
+    // For each message check if there was an error.
+    const tokensToRemove = [];
+    response.results.forEach((result, index) => {
+      const error = result.error;
+      if (error) {
+        console.error('Failure sending notification to', tokens[index], error);
+        // Cleanup the tokens who are not registered anymore.
+        if (error.code === 'messaging/invalid-registration-token' || error.code === 'messaging/registration-token-not-registered') {
+          tokensToRemove.push(tokensSnapshot.ref.child(tokens[index]).remove());
         }
-      });
-      return Promise.all(tokensToRemove);
+      }
     });
+    return Promise.all(tokensToRemove);
   });
 });
diff --git a/ffmpeg-convert-audio/functions/.eslintrc.json b/ffmpeg-convert-audio/functions/.eslintrc.json
new file mode 100644
index 0000000000..eb4c93169b
--- /dev/null
+++ b/ffmpeg-convert-audio/functions/.eslintrc.json
@@ -0,0 +1,125 @@
+{
+  "parserOptions": {
+    // Required for certain syntax usages
+    "ecmaVersion": 6
+  },
+  "plugins": [
+    "promise"
+  ],
+  "extends": "eslint:recommended",
+  "rules": {
+    // Removed rule "disallow the use of console" from recommended eslint rules
+    "no-console": "off",
+
+    // Removed rule "disallow multiple spaces in regular expressions" from recommended eslint rules
+    "no-regex-spaces": "off",
+
+    // Removed rule "disallow the use of debugger" from recommended eslint rules
+    "no-debugger": "off",
+
+    // Removed rule "disallow unused variables" from recommended eslint rules
+    "no-unused-vars": "off",
+
+    // Removed rule "disallow mixed spaces and tabs for indentation" from recommended eslint rules
+    "no-mixed-spaces-and-tabs": "off",
+
+    // Removed rule "disallow the use of undeclared variables unless mentioned in /*global */ comments" from recommended eslint rules
+    "no-undef": "off",
+
+    // Warn against template literal placeholder syntax in regular strings
+    "no-template-curly-in-string": 1,
+
+    // Warn if return statements do not either always or never specify values
+    "consistent-return": 1,
+
+    // Warn if no return statements in callbacks of array methods
+    "array-callback-return": 1,
+
+    // Requre the use of === and !==
+    "eqeqeq": 2,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    // Disallow the use of alert, confirm, and prompt
+    "no-alert": 2,
+
+    // Disallow the use of arguments.caller or arguments.callee
+    "no-caller": 2,
+
+    // Disallow null comparisons without type-checking operators
+    "no-eq-null": 2,
+
+    // Disallow the use of eval()
+    "no-eval": 2,
+
+    // Warn against extending native types
+    "no-extend-native": 1,
+
+    // Warn against unnecessary calls to .bind()
+    "no-extra-bind": 1,
+
+    // Warn against unnecessary labels    
+    "no-extra-label": 1,
+
+    // Disallow leading or trailing decimal points in numeric literals
+    "no-floating-decimal": 2,
+
+    // Warn against shorthand type conversions
+    "no-implicit-coercion": 1,
+
+    // Warn against function declarations and expressions inside loop statements
+    "no-loop-func": 1,
+
+    // Disallow new operators with the Function object
+    "no-new-func": 2,
+
+    // Warn against new operators with the String, Number, and Boolean objects
+    "no-new-wrappers": 1,
+
+    // Disallow throwing literals as exceptions
+    "no-throw-literal": 2,
+
+    // Require using Error objects as Promise rejection reasons
+    "prefer-promise-reject-errors": 2,
+
+    // Enforce “for” loop update clause moving the counter in the right direction
+    "for-direction": 2,
+
+    // Enforce return statements in getters
+    "getter-return": 2,
+
+    // Disallow await inside of loops
+    "no-await-in-loop": 2,
+
+    // Disallow comparing against -0
+    "no-compare-neg-zero": 2,
+
+    // Warn against catch clause parameters from shadowing variables in the outer scope
+    "no-catch-shadow": 1,
+
+    // Disallow identifiers from shadowing restricted names
+    "no-shadow-restricted-names": 2,
+
+    // Enforce return statements in callbacks of array methods
+    "callback-return": 2,
+
+    // Require error handling in callbacks
+    "handle-callback-err": 2,
+
+    // Warn against string concatenation with __dirname and __filename
+    "no-path-concat": 1,
+
+    // Prefer using arrow functions for callbacks
+    "prefer-arrow-callback": 1,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    //Enforces the use of catch() on un-returned promises
+    "promise/catch-or-return": 2,
+
+    // Warn against nested then() or catch() statements
+    "promise/no-nesting": 1
+  }
+}
diff --git a/ffmpeg-convert-audio/functions/index.js b/ffmpeg-convert-audio/functions/index.js
index 49e86275bb..96b7fc4fbf 100644
--- a/ffmpeg-convert-audio/functions/index.js
+++ b/ffmpeg-convert-audio/functions/index.js
@@ -26,21 +26,42 @@ const ffmpeg_static = require('ffmpeg-static');
 function promisifyCommand(command) {
   return new Promise((resolve, reject) => {
     command
-      .on('end', () => {
-        resolve();
-      })
-      .on('error', error => {
-        reject(error);
-      })
-      .run();
-   });
- };
+        .on('end', () => {
+          resolve();
+        })
+        .on('error', (error) => {
+          reject(error);
+        })
+        .run();
+  });
+}
+
+/**
+ * Utility method to convert audio to mono channel using FFMPEG.
+ */
+function reencodeAsync(tempFilePath, targetTempFilePath) {
+  return new Promise((resolve, reject) => {
+    const command = ffmpeg(tempFilePath)
+        .setFfmpegPath(ffmpeg_static.path)
+        .audioChannels(1)
+        .audioFrequency(16000)
+        .format('flac')
+        .on('error', (err) => {
+          console.log('An error occurred: ' + err.message);
+          reject(err);
+        })
+        .on('end', () => {
+          console.log('Output audio created at', targetTempFilePath);
+        })
+        .save(targetTempFilePath);
+  });
+}
 
 /**
  * When an audio is uploaded in the Storage bucket We generate a mono channel audio automatically using
  * node-fluent-ffmpeg.
  */
-exports.generateMonoAudio = functions.storage.object().onChange(event => {
+exports.generateMonoAudio = functions.storage.object().onChange((event) => {
   const object = event.data; // The Storage object.
 
   const fileBucket = object.bucket; // The Storage bucket that contains the file.
@@ -52,7 +73,7 @@ exports.generateMonoAudio = functions.storage.object().onChange(event => {
   // Exit if this is triggered on a file that is not an audio.
   if (!contentType.startsWith('audio/')) {
     console.log('This is not an audio.');
-    return;
+    return null;
   }
 
   // Get the file name.
@@ -60,57 +81,57 @@ exports.generateMonoAudio = functions.storage.object().onChange(event => {
   // Exit if the audio is already converted.
   if (fileName.endsWith('_output.flac')) {
     console.log('Already a converted audio.');
-    return;
+    return null;
   }
 
   // Exit if this is a move or deletion event.
   if (resourceState === 'not_exists') {
     console.log('This is a deletion event.');
-    return;
+    return null;
   }
 
   // Exit if file exists but is not new and is only being triggered
   // because of a metadata change.
   if (resourceState === 'exists' && metageneration > 1) {
     console.log('This is a metadata change event.');
-    return;
+    return null;
   }
 
   // Download file from bucket.
   const bucket = gcs.bucket(fileBucket);
   const tempFilePath = path.join(os.tmpdir(), fileName);
   // We add a '_output.flac' suffix to target audio file name. That's where we'll upload the converted audio.
-  const targetTempFileName = fileName.replace(/\.[^/.]+$/, "") + '_output.flac';
+  const targetTempFileName = fileName.replace(/\.[^/.]+$/, '') + '_output.flac';
   const targetTempFilePath = path.join(os.tmpdir(), targetTempFileName);
   const targetStorageFilePath = path.join(path.dirname(filePath), targetTempFileName);
 
   return bucket.file(filePath).download({
-    destination: tempFilePath
+    destination: tempFilePath,
   }).then(() => {
     console.log('Audio downloaded locally to', tempFilePath);
     // Convert the audio to mono channel using FFMPEG.
 
     let command = ffmpeg(tempFilePath)
-      .setFfmpegPath(ffmpeg_static.path)
-      .audioChannels(1)
-      .audioFrequency(16000)
-      .format('flac')
-      .output(targetTempFilePath);
+        .setFfmpegPath(ffmpeg_static.path)
+        .audioChannels(1)
+        .audioFrequency(16000)
+        .format('flac')
+        .output(targetTempFilePath);
 
     command = promisifyCommand(command);
 
-    return command.then(() => {
-      console.log('Output audio created at', targetTempFilePath);
-      // Uploading the audio.
-      return bucket.upload(targetTempFilePath, { destination: targetStorageFilePath }).then(() => {
-        console.log('Output audio uploaded to', targetStorageFilePath);
+    return command;
+  }).then(() => {
+    console.log('Output audio created at', targetTempFilePath);
+    // Uploading the audio.
+    return bucket.upload(targetTempFilePath, {destination: targetStorageFilePath});
+  }).then(() => {
+    console.log('Output audio uploaded to', targetStorageFilePath);
 
-        // Once the audio has been uploaded delete the local file to free up disk space.
-        fs.unlinkSync(tempFilePath);
-        fs.unlinkSync(targetTempFilePath);
+    // Once the audio has been uploaded delete the local file to free up disk space.
+    fs.unlinkSync(tempFilePath);
+    fs.unlinkSync(targetTempFilePath);
 
-        console.log('Temporary files removed.', targetTempFilePath);
-      });
-    });
+    return console.log('Temporary files removed.', targetTempFilePath);
   });
 });
diff --git a/fulltext-search-firestore/functions/.eslintrc.json b/fulltext-search-firestore/functions/.eslintrc.json
new file mode 100644
index 0000000000..eb4c93169b
--- /dev/null
+++ b/fulltext-search-firestore/functions/.eslintrc.json
@@ -0,0 +1,125 @@
+{
+  "parserOptions": {
+    // Required for certain syntax usages
+    "ecmaVersion": 6
+  },
+  "plugins": [
+    "promise"
+  ],
+  "extends": "eslint:recommended",
+  "rules": {
+    // Removed rule "disallow the use of console" from recommended eslint rules
+    "no-console": "off",
+
+    // Removed rule "disallow multiple spaces in regular expressions" from recommended eslint rules
+    "no-regex-spaces": "off",
+
+    // Removed rule "disallow the use of debugger" from recommended eslint rules
+    "no-debugger": "off",
+
+    // Removed rule "disallow unused variables" from recommended eslint rules
+    "no-unused-vars": "off",
+
+    // Removed rule "disallow mixed spaces and tabs for indentation" from recommended eslint rules
+    "no-mixed-spaces-and-tabs": "off",
+
+    // Removed rule "disallow the use of undeclared variables unless mentioned in /*global */ comments" from recommended eslint rules
+    "no-undef": "off",
+
+    // Warn against template literal placeholder syntax in regular strings
+    "no-template-curly-in-string": 1,
+
+    // Warn if return statements do not either always or never specify values
+    "consistent-return": 1,
+
+    // Warn if no return statements in callbacks of array methods
+    "array-callback-return": 1,
+
+    // Requre the use of === and !==
+    "eqeqeq": 2,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    // Disallow the use of alert, confirm, and prompt
+    "no-alert": 2,
+
+    // Disallow the use of arguments.caller or arguments.callee
+    "no-caller": 2,
+
+    // Disallow null comparisons without type-checking operators
+    "no-eq-null": 2,
+
+    // Disallow the use of eval()
+    "no-eval": 2,
+
+    // Warn against extending native types
+    "no-extend-native": 1,
+
+    // Warn against unnecessary calls to .bind()
+    "no-extra-bind": 1,
+
+    // Warn against unnecessary labels    
+    "no-extra-label": 1,
+
+    // Disallow leading or trailing decimal points in numeric literals
+    "no-floating-decimal": 2,
+
+    // Warn against shorthand type conversions
+    "no-implicit-coercion": 1,
+
+    // Warn against function declarations and expressions inside loop statements
+    "no-loop-func": 1,
+
+    // Disallow new operators with the Function object
+    "no-new-func": 2,
+
+    // Warn against new operators with the String, Number, and Boolean objects
+    "no-new-wrappers": 1,
+
+    // Disallow throwing literals as exceptions
+    "no-throw-literal": 2,
+
+    // Require using Error objects as Promise rejection reasons
+    "prefer-promise-reject-errors": 2,
+
+    // Enforce “for” loop update clause moving the counter in the right direction
+    "for-direction": 2,
+
+    // Enforce return statements in getters
+    "getter-return": 2,
+
+    // Disallow await inside of loops
+    "no-await-in-loop": 2,
+
+    // Disallow comparing against -0
+    "no-compare-neg-zero": 2,
+
+    // Warn against catch clause parameters from shadowing variables in the outer scope
+    "no-catch-shadow": 1,
+
+    // Disallow identifiers from shadowing restricted names
+    "no-shadow-restricted-names": 2,
+
+    // Enforce return statements in callbacks of array methods
+    "callback-return": 2,
+
+    // Require error handling in callbacks
+    "handle-callback-err": 2,
+
+    // Warn against string concatenation with __dirname and __filename
+    "no-path-concat": 1,
+
+    // Prefer using arrow functions for callbacks
+    "prefer-arrow-callback": 1,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    //Enforces the use of catch() on un-returned promises
+    "promise/catch-or-return": 2,
+
+    // Warn against nested then() or catch() statements
+    "promise/no-nesting": 1
+  }
+}
diff --git a/fulltext-search-firestore/functions/index.js b/fulltext-search-firestore/functions/index.js
index 1457b93952..f6bd4fed4f 100644
--- a/fulltext-search-firestore/functions/index.js
+++ b/fulltext-search-firestore/functions/index.js
@@ -31,7 +31,7 @@ const client = algoliasearch(ALGOLIA_ID, ALGOLIA_ADMIN_KEY);
 
 // [START update_index_function]
 // Update the search index every time a blog post is written.
-exports.onNoteCreated = functions.firestore.document('notes/{noteId}').onCreate(event => {
+exports.onNoteCreated = functions.firestore.document('notes/{noteId}').onCreate((event) => {
   // Get the note document
   const note = event.data.data();
 
@@ -51,37 +51,31 @@ admin.initializeApp(functions.config().firebase);
 function getFirebaseUser(req, res, next) {
   console.log('Check if request is authorized with Firebase ID token');
 
-  if (!req.headers.authorization
-      || !req.headers.authorization.startsWith('Bearer ')) {
+  if (!req.headers.authorization || !req.headers.authorization.startsWith('Bearer ')) {
     console.error(
       'No Firebase ID token was passed as a Bearer token in the Authorization header.',
       'Make sure you authorize your request by providing the following HTTP header:',
       'Authorization: Bearer <Firebase ID Token>'
-    );
-    res.status(403).send('Unauthorized');
-    return;
+      );
+    return res.sendStatus(403);
   }
 
   let idToken;
-  if (
-    req.headers.authorization &&
-    req.headers.authorization.startsWith('Bearer ')
-  ) {
-    console.log('Found 'Authorization' header');
+  if (req.headers.authorization && req.headers.authorization.startsWith('Bearer ')) {
+    console.log('Found \'Authorization\' header');
     idToken = req.headers.authorization.split('Bearer ')[1];
   }
 
-  admin
+  return admin
     .auth()
     .verifyIdToken(idToken)
-    .then(decodedIdToken => {
+    .then((decodedIdToken) => {
       console.log('ID Token correctly decoded', decodedIdToken);
       req.user = decodedIdToken;
-      next();
-    })
-    .catch(error => {
+      return next();
+    }).catch((error) => {
       console.error('Error while verifying Firebase ID token:', error);
-      res.status(403).send('Unauthorized');
+      return res.status(403).send('Unauthorized');
     });
 }
 // [END get_firebase_user]
@@ -93,7 +87,7 @@ const app = require('express')();
 
 // We'll enable CORS support to allow the function to be invoked
 // from our app client-side.
-app.use(require('cors')({ origin: true }));
+app.use(require('cors')({origin: true}));
 
 // Then we'll also use a special 'getFirebaseUser' middleware which
 // verifies the Authorization header and adds a `user` field to the
@@ -101,7 +95,7 @@ app.use(require('cors')({ origin: true }));
 // https://gist.github.com/abehaskins/832d6f8665454d0cd99ef08c229afb42
 app.use(getFirebaseUser);
 
-// Add a route handler to the app to generate the secured key 
+// Add a route handler to the app to generate the secured key
 app.get('/', (req, res) => {
   // Create the params object as described in the Algolia documentation:
   // https://www.algolia.com/doc/guides/security/api-keys/#generating-api-keys
@@ -109,14 +103,14 @@ app.get('/', (req, res) => {
     // This filter ensures that only documents where author == user_id will be readable
     filters: `author:${req.user.user_id}`,
     // We also proxy the user_id as a unique token for this key.
-    userToken: req.user.user_id
+    userToken: req.user.user_id,
   };
 
   // Call the Algolia API to generate a unique key based on our search key
   const key = client.generateSecuredApiKey(ALGOLIA_SEARCH_KEY, params);
 
   // Then return this key as {key: '...key'}
-  res.json({ key });
+  res.json({key});
 });
 
 // Finally, pass our ExpressJS app to Cloud Functions as a function
diff --git a/fulltext-search/functions/.eslintrc.json b/fulltext-search/functions/.eslintrc.json
new file mode 100644
index 0000000000..eb4c93169b
--- /dev/null
+++ b/fulltext-search/functions/.eslintrc.json
@@ -0,0 +1,125 @@
+{
+  "parserOptions": {
+    // Required for certain syntax usages
+    "ecmaVersion": 6
+  },
+  "plugins": [
+    "promise"
+  ],
+  "extends": "eslint:recommended",
+  "rules": {
+    // Removed rule "disallow the use of console" from recommended eslint rules
+    "no-console": "off",
+
+    // Removed rule "disallow multiple spaces in regular expressions" from recommended eslint rules
+    "no-regex-spaces": "off",
+
+    // Removed rule "disallow the use of debugger" from recommended eslint rules
+    "no-debugger": "off",
+
+    // Removed rule "disallow unused variables" from recommended eslint rules
+    "no-unused-vars": "off",
+
+    // Removed rule "disallow mixed spaces and tabs for indentation" from recommended eslint rules
+    "no-mixed-spaces-and-tabs": "off",
+
+    // Removed rule "disallow the use of undeclared variables unless mentioned in /*global */ comments" from recommended eslint rules
+    "no-undef": "off",
+
+    // Warn against template literal placeholder syntax in regular strings
+    "no-template-curly-in-string": 1,
+
+    // Warn if return statements do not either always or never specify values
+    "consistent-return": 1,
+
+    // Warn if no return statements in callbacks of array methods
+    "array-callback-return": 1,
+
+    // Requre the use of === and !==
+    "eqeqeq": 2,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    // Disallow the use of alert, confirm, and prompt
+    "no-alert": 2,
+
+    // Disallow the use of arguments.caller or arguments.callee
+    "no-caller": 2,
+
+    // Disallow null comparisons without type-checking operators
+    "no-eq-null": 2,
+
+    // Disallow the use of eval()
+    "no-eval": 2,
+
+    // Warn against extending native types
+    "no-extend-native": 1,
+
+    // Warn against unnecessary calls to .bind()
+    "no-extra-bind": 1,
+
+    // Warn against unnecessary labels    
+    "no-extra-label": 1,
+
+    // Disallow leading or trailing decimal points in numeric literals
+    "no-floating-decimal": 2,
+
+    // Warn against shorthand type conversions
+    "no-implicit-coercion": 1,
+
+    // Warn against function declarations and expressions inside loop statements
+    "no-loop-func": 1,
+
+    // Disallow new operators with the Function object
+    "no-new-func": 2,
+
+    // Warn against new operators with the String, Number, and Boolean objects
+    "no-new-wrappers": 1,
+
+    // Disallow throwing literals as exceptions
+    "no-throw-literal": 2,
+
+    // Require using Error objects as Promise rejection reasons
+    "prefer-promise-reject-errors": 2,
+
+    // Enforce “for” loop update clause moving the counter in the right direction
+    "for-direction": 2,
+
+    // Enforce return statements in getters
+    "getter-return": 2,
+
+    // Disallow await inside of loops
+    "no-await-in-loop": 2,
+
+    // Disallow comparing against -0
+    "no-compare-neg-zero": 2,
+
+    // Warn against catch clause parameters from shadowing variables in the outer scope
+    "no-catch-shadow": 1,
+
+    // Disallow identifiers from shadowing restricted names
+    "no-shadow-restricted-names": 2,
+
+    // Enforce return statements in callbacks of array methods
+    "callback-return": 2,
+
+    // Require error handling in callbacks
+    "handle-callback-err": 2,
+
+    // Warn against string concatenation with __dirname and __filename
+    "no-path-concat": 1,
+
+    // Prefer using arrow functions for callbacks
+    "prefer-arrow-callback": 1,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    //Enforces the use of catch() on un-returned promises
+    "promise/catch-or-return": 2,
+
+    // Warn against nested then() or catch() statements
+    "promise/no-nesting": 1
+  }
+}
diff --git a/fulltext-search/functions/index.js b/fulltext-search/functions/index.js
index ad5d06bbae..b90b63bec8 100644
--- a/fulltext-search/functions/index.js
+++ b/fulltext-search/functions/index.js
@@ -28,11 +28,11 @@ const client = algoliasearch(functions.config().algolia.app_id, functions.config
 const ALGOLIA_POSTS_INDEX_NAME = 'blogposts';
 
 // Updates the search index when new blog entries are created or updated.
-exports.indexentry = functions.database.ref('/blog-posts/{blogid}/text').onWrite(event => {
+exports.indexentry = functions.database.ref('/blog-posts/{blogid}/text').onWrite((event) => {
   const index = client.initIndex(ALGOLIA_POSTS_INDEX_NAME);
   const firebaseObject = {
     text: event.data.val(),
-    objectID: event.params.blogid
+    objectID: event.params.blogid,
   };
 
   return index.saveObject(firebaseObject).then(
@@ -42,15 +42,15 @@ exports.indexentry = functions.database.ref('/blog-posts/{blogid}/text').onWrite
 
 // Starts a search query whenever a query is requested (by adding one to the `/search/queries`
 // element. Search results are then written under `/search/results`.
-exports.searchentry = functions.database.ref('/search/queries/{queryid}').onWrite(event => {
+exports.searchentry = functions.database.ref('/search/queries/{queryid}').onWrite((event) => {
   const index = client.initIndex(ALGOLIA_POSTS_INDEX_NAME);
 
   const query = event.data.val().query;
   const key = event.data.key;
 
-  return index.search(query).then(content => {
+  return index.search(query).then((content) => {
     const updates = {
-      '/search/last_query_timestamp': Date.parse(event.timestamp)
+      '/search/last_query_timestamp': Date.parse(event.timestamp),
     };
     updates[`/search/results/${key}`] = content;
     return admin.database().ref().update(updates);
diff --git a/generate-thumbnail/functions/.eslintrc.json b/generate-thumbnail/functions/.eslintrc.json
new file mode 100644
index 0000000000..eb4c93169b
--- /dev/null
+++ b/generate-thumbnail/functions/.eslintrc.json
@@ -0,0 +1,125 @@
+{
+  "parserOptions": {
+    // Required for certain syntax usages
+    "ecmaVersion": 6
+  },
+  "plugins": [
+    "promise"
+  ],
+  "extends": "eslint:recommended",
+  "rules": {
+    // Removed rule "disallow the use of console" from recommended eslint rules
+    "no-console": "off",
+
+    // Removed rule "disallow multiple spaces in regular expressions" from recommended eslint rules
+    "no-regex-spaces": "off",
+
+    // Removed rule "disallow the use of debugger" from recommended eslint rules
+    "no-debugger": "off",
+
+    // Removed rule "disallow unused variables" from recommended eslint rules
+    "no-unused-vars": "off",
+
+    // Removed rule "disallow mixed spaces and tabs for indentation" from recommended eslint rules
+    "no-mixed-spaces-and-tabs": "off",
+
+    // Removed rule "disallow the use of undeclared variables unless mentioned in /*global */ comments" from recommended eslint rules
+    "no-undef": "off",
+
+    // Warn against template literal placeholder syntax in regular strings
+    "no-template-curly-in-string": 1,
+
+    // Warn if return statements do not either always or never specify values
+    "consistent-return": 1,
+
+    // Warn if no return statements in callbacks of array methods
+    "array-callback-return": 1,
+
+    // Requre the use of === and !==
+    "eqeqeq": 2,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    // Disallow the use of alert, confirm, and prompt
+    "no-alert": 2,
+
+    // Disallow the use of arguments.caller or arguments.callee
+    "no-caller": 2,
+
+    // Disallow null comparisons without type-checking operators
+    "no-eq-null": 2,
+
+    // Disallow the use of eval()
+    "no-eval": 2,
+
+    // Warn against extending native types
+    "no-extend-native": 1,
+
+    // Warn against unnecessary calls to .bind()
+    "no-extra-bind": 1,
+
+    // Warn against unnecessary labels    
+    "no-extra-label": 1,
+
+    // Disallow leading or trailing decimal points in numeric literals
+    "no-floating-decimal": 2,
+
+    // Warn against shorthand type conversions
+    "no-implicit-coercion": 1,
+
+    // Warn against function declarations and expressions inside loop statements
+    "no-loop-func": 1,
+
+    // Disallow new operators with the Function object
+    "no-new-func": 2,
+
+    // Warn against new operators with the String, Number, and Boolean objects
+    "no-new-wrappers": 1,
+
+    // Disallow throwing literals as exceptions
+    "no-throw-literal": 2,
+
+    // Require using Error objects as Promise rejection reasons
+    "prefer-promise-reject-errors": 2,
+
+    // Enforce “for” loop update clause moving the counter in the right direction
+    "for-direction": 2,
+
+    // Enforce return statements in getters
+    "getter-return": 2,
+
+    // Disallow await inside of loops
+    "no-await-in-loop": 2,
+
+    // Disallow comparing against -0
+    "no-compare-neg-zero": 2,
+
+    // Warn against catch clause parameters from shadowing variables in the outer scope
+    "no-catch-shadow": 1,
+
+    // Disallow identifiers from shadowing restricted names
+    "no-shadow-restricted-names": 2,
+
+    // Enforce return statements in callbacks of array methods
+    "callback-return": 2,
+
+    // Require error handling in callbacks
+    "handle-callback-err": 2,
+
+    // Warn against string concatenation with __dirname and __filename
+    "no-path-concat": 1,
+
+    // Prefer using arrow functions for callbacks
+    "prefer-arrow-callback": 1,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    //Enforces the use of catch() on un-returned promises
+    "promise/catch-or-return": 2,
+
+    // Warn against nested then() or catch() statements
+    "promise/no-nesting": 1
+  }
+}
diff --git a/generate-thumbnail/functions/index.js b/generate-thumbnail/functions/index.js
index 190006e0d0..bee0ec6703 100644
--- a/generate-thumbnail/functions/index.js
+++ b/generate-thumbnail/functions/index.js
@@ -38,7 +38,7 @@ const THUMB_PREFIX = 'thumb_';
  * After the thumbnail has been generated and uploaded to Cloud Storage,
  * we write the public URL to the Firebase Realtime Database.
  */
-exports.generateThumbnail = functions.storage.object().onChange(event => {
+exports.generateThumbnail = functions.storage.object().onChange((event) => {
   // File and directory paths.
   const filePath = event.data.name;
   const contentType = event.data.contentType; // This is the image Mimme type
@@ -71,7 +71,7 @@ exports.generateThumbnail = functions.storage.object().onChange(event => {
   const bucket = gcs.bucket(event.data.bucket);
   const file = bucket.file(filePath);
   const thumbFile = bucket.file(thumbFilePath);
-  const metadata = { contentType: contentType };
+  const metadata = {contentType: contentType};
 
   // Create the temp directory where the storage file will be downloaded.
   return mkdirp(tempLocalDir).then(() => {
@@ -84,7 +84,7 @@ exports.generateThumbnail = functions.storage.object().onChange(event => {
   }).then(() => {
     console.log('Thumbnail created at', tempLocalThumbFile);
     // Uploading the Thumbnail.
-    return bucket.upload(tempLocalThumbFile, { destination: thumbFilePath, metadata: metadata });
+    return bucket.upload(tempLocalThumbFile, {destination: thumbFilePath, metadata: metadata});
   }).then(() => {
     console.log('Thumbnail uploaded to Storage at', thumbFilePath);
     // Once the image has been uploaded delete the local files to free up disk space.
@@ -93,13 +93,13 @@ exports.generateThumbnail = functions.storage.object().onChange(event => {
     // Get the Signed URLs for the thumbnail and original image.
     const config = {
       action: 'read',
-      expires: '03-01-2500'
+      expires: '03-01-2500',
     };
     return Promise.all([
       thumbFile.getSignedUrl(config),
-      file.getSignedUrl(config)
+      file.getSignedUrl(config),
     ]);
-  }).then(results => {
+  }).then((results) => {
     console.log('Got Signed URLs.');
     const thumbResult = results[0];
     const originalResult = results[1];
diff --git a/github-to-slack/functions/.eslintrc.json b/github-to-slack/functions/.eslintrc.json
new file mode 100644
index 0000000000..eb4c93169b
--- /dev/null
+++ b/github-to-slack/functions/.eslintrc.json
@@ -0,0 +1,125 @@
+{
+  "parserOptions": {
+    // Required for certain syntax usages
+    "ecmaVersion": 6
+  },
+  "plugins": [
+    "promise"
+  ],
+  "extends": "eslint:recommended",
+  "rules": {
+    // Removed rule "disallow the use of console" from recommended eslint rules
+    "no-console": "off",
+
+    // Removed rule "disallow multiple spaces in regular expressions" from recommended eslint rules
+    "no-regex-spaces": "off",
+
+    // Removed rule "disallow the use of debugger" from recommended eslint rules
+    "no-debugger": "off",
+
+    // Removed rule "disallow unused variables" from recommended eslint rules
+    "no-unused-vars": "off",
+
+    // Removed rule "disallow mixed spaces and tabs for indentation" from recommended eslint rules
+    "no-mixed-spaces-and-tabs": "off",
+
+    // Removed rule "disallow the use of undeclared variables unless mentioned in /*global */ comments" from recommended eslint rules
+    "no-undef": "off",
+
+    // Warn against template literal placeholder syntax in regular strings
+    "no-template-curly-in-string": 1,
+
+    // Warn if return statements do not either always or never specify values
+    "consistent-return": 1,
+
+    // Warn if no return statements in callbacks of array methods
+    "array-callback-return": 1,
+
+    // Requre the use of === and !==
+    "eqeqeq": 2,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    // Disallow the use of alert, confirm, and prompt
+    "no-alert": 2,
+
+    // Disallow the use of arguments.caller or arguments.callee
+    "no-caller": 2,
+
+    // Disallow null comparisons without type-checking operators
+    "no-eq-null": 2,
+
+    // Disallow the use of eval()
+    "no-eval": 2,
+
+    // Warn against extending native types
+    "no-extend-native": 1,
+
+    // Warn against unnecessary calls to .bind()
+    "no-extra-bind": 1,
+
+    // Warn against unnecessary labels    
+    "no-extra-label": 1,
+
+    // Disallow leading or trailing decimal points in numeric literals
+    "no-floating-decimal": 2,
+
+    // Warn against shorthand type conversions
+    "no-implicit-coercion": 1,
+
+    // Warn against function declarations and expressions inside loop statements
+    "no-loop-func": 1,
+
+    // Disallow new operators with the Function object
+    "no-new-func": 2,
+
+    // Warn against new operators with the String, Number, and Boolean objects
+    "no-new-wrappers": 1,
+
+    // Disallow throwing literals as exceptions
+    "no-throw-literal": 2,
+
+    // Require using Error objects as Promise rejection reasons
+    "prefer-promise-reject-errors": 2,
+
+    // Enforce “for” loop update clause moving the counter in the right direction
+    "for-direction": 2,
+
+    // Enforce return statements in getters
+    "getter-return": 2,
+
+    // Disallow await inside of loops
+    "no-await-in-loop": 2,
+
+    // Disallow comparing against -0
+    "no-compare-neg-zero": 2,
+
+    // Warn against catch clause parameters from shadowing variables in the outer scope
+    "no-catch-shadow": 1,
+
+    // Disallow identifiers from shadowing restricted names
+    "no-shadow-restricted-names": 2,
+
+    // Enforce return statements in callbacks of array methods
+    "callback-return": 2,
+
+    // Require error handling in callbacks
+    "handle-callback-err": 2,
+
+    // Warn against string concatenation with __dirname and __filename
+    "no-path-concat": 1,
+
+    // Prefer using arrow functions for callbacks
+    "prefer-arrow-callback": 1,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    //Enforces the use of catch() on un-returned promises
+    "promise/catch-or-return": 2,
+
+    // Warn against nested then() or catch() statements
+    "promise/no-nesting": 1
+  }
+}
diff --git a/github-to-slack/functions/index.js b/github-to-slack/functions/index.js
index 9b241541fb..7c60d5c922 100644
--- a/github-to-slack/functions/index.js
+++ b/github-to-slack/functions/index.js
@@ -30,23 +30,21 @@ exports.githubWebhook = functions.https.onRequest((req, res) => {
 
   // TODO: Configure the `github.secret` Google Cloud environment variables.
   const hmac = crypto.createHmac(cipher, functions.config().github.secret)
-      // The JSON body is automatically parsed by Cloud Functions so we re-stringify it.
-      .update(JSON.stringify(req.body, null, 0))
-      .digest('hex');
+    .update(req.body)
+    .digest('hex');
   const expectedSignature = `${cipher}=${hmac}`;
 
   // Check that the body of the request has been signed with the GitHub Secret.
-  if (secureCompare(signature, expectedSignature)) {
-    postToSlack(req.body.compare, req.body.commits.length, req.body.repository).then(() => {
-      res.end();
-    }).catch(error => {
-      console.error(error);
-      res.status(500).send('Something went wrong while posting the message to Slack.');
-    });
-  } else {
+  if (!secureCompare(signature, expectedSignature)) {
     console.error('x-hub-signature', signature, 'did not match', expectedSignature);
-    res.status(403).send('Your x-hub-signature\'s bad and you should feel bad!');
+    return res.status(403).send('Your x-hub-signature\'s bad and you should feel bad!');
   }
+  return postToSlack(req.body.compare, req.body.commits.length, req.body.repository).then(() => {
+    return res.end();
+  }).catch((error) => {
+    console.error(error);
+    return res.status(500).send('Something went wrong while posting the message to Slack.');
+  });
 });
 
 /**
@@ -58,8 +56,8 @@ function postToSlack(url, commits, repo) {
     // TODO: Configure the `slack.webhook_url` Google Cloud environment variables.
     uri: functions.config().slack.webhook_url,
     body: {
-      text: `<${url}|${commits} new commit${commits > 1 ? 's' : ''}> pushed to <${repo.url}|${repo.full_name}>.`
+      text: `<${url}|${commits} new commit${commits > 1 ? 's' : ''}> pushed to <${repo.url}|${repo.full_name}>.`,
     },
-    json: true
+    json: true,
   });
 }
diff --git a/google-sheet-sync/functions/.eslintrc.json b/google-sheet-sync/functions/.eslintrc.json
new file mode 100644
index 0000000000..eb4c93169b
--- /dev/null
+++ b/google-sheet-sync/functions/.eslintrc.json
@@ -0,0 +1,125 @@
+{
+  "parserOptions": {
+    // Required for certain syntax usages
+    "ecmaVersion": 6
+  },
+  "plugins": [
+    "promise"
+  ],
+  "extends": "eslint:recommended",
+  "rules": {
+    // Removed rule "disallow the use of console" from recommended eslint rules
+    "no-console": "off",
+
+    // Removed rule "disallow multiple spaces in regular expressions" from recommended eslint rules
+    "no-regex-spaces": "off",
+
+    // Removed rule "disallow the use of debugger" from recommended eslint rules
+    "no-debugger": "off",
+
+    // Removed rule "disallow unused variables" from recommended eslint rules
+    "no-unused-vars": "off",
+
+    // Removed rule "disallow mixed spaces and tabs for indentation" from recommended eslint rules
+    "no-mixed-spaces-and-tabs": "off",
+
+    // Removed rule "disallow the use of undeclared variables unless mentioned in /*global */ comments" from recommended eslint rules
+    "no-undef": "off",
+
+    // Warn against template literal placeholder syntax in regular strings
+    "no-template-curly-in-string": 1,
+
+    // Warn if return statements do not either always or never specify values
+    "consistent-return": 1,
+
+    // Warn if no return statements in callbacks of array methods
+    "array-callback-return": 1,
+
+    // Requre the use of === and !==
+    "eqeqeq": 2,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    // Disallow the use of alert, confirm, and prompt
+    "no-alert": 2,
+
+    // Disallow the use of arguments.caller or arguments.callee
+    "no-caller": 2,
+
+    // Disallow null comparisons without type-checking operators
+    "no-eq-null": 2,
+
+    // Disallow the use of eval()
+    "no-eval": 2,
+
+    // Warn against extending native types
+    "no-extend-native": 1,
+
+    // Warn against unnecessary calls to .bind()
+    "no-extra-bind": 1,
+
+    // Warn against unnecessary labels    
+    "no-extra-label": 1,
+
+    // Disallow leading or trailing decimal points in numeric literals
+    "no-floating-decimal": 2,
+
+    // Warn against shorthand type conversions
+    "no-implicit-coercion": 1,
+
+    // Warn against function declarations and expressions inside loop statements
+    "no-loop-func": 1,
+
+    // Disallow new operators with the Function object
+    "no-new-func": 2,
+
+    // Warn against new operators with the String, Number, and Boolean objects
+    "no-new-wrappers": 1,
+
+    // Disallow throwing literals as exceptions
+    "no-throw-literal": 2,
+
+    // Require using Error objects as Promise rejection reasons
+    "prefer-promise-reject-errors": 2,
+
+    // Enforce “for” loop update clause moving the counter in the right direction
+    "for-direction": 2,
+
+    // Enforce return statements in getters
+    "getter-return": 2,
+
+    // Disallow await inside of loops
+    "no-await-in-loop": 2,
+
+    // Disallow comparing against -0
+    "no-compare-neg-zero": 2,
+
+    // Warn against catch clause parameters from shadowing variables in the outer scope
+    "no-catch-shadow": 1,
+
+    // Disallow identifiers from shadowing restricted names
+    "no-shadow-restricted-names": 2,
+
+    // Enforce return statements in callbacks of array methods
+    "callback-return": 2,
+
+    // Require error handling in callbacks
+    "handle-callback-err": 2,
+
+    // Warn against string concatenation with __dirname and __filename
+    "no-path-concat": 1,
+
+    // Prefer using arrow functions for callbacks
+    "prefer-arrow-callback": 1,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    //Enforces the use of catch() on un-returned promises
+    "promise/catch-or-return": 2,
+
+    // Warn against nested then() or catch() statements
+    "promise/no-nesting": 1
+  }
+}
diff --git a/google-sheet-sync/functions/index.js b/google-sheet-sync/functions/index.js
index 89bed27d3e..9c11b5bf3a 100644
--- a/google-sheet-sync/functions/index.js
+++ b/google-sheet-sync/functions/index.js
@@ -19,15 +19,15 @@
 
 const functions = require('firebase-functions');
 const admin = require('firebase-admin');
-const { OAuth2Client } = require('google-auth-library');
+const {OAuth2Client} = require('google-auth-library');
 const google = require('googleapis');
 
 admin.initializeApp(functions.config().firebase);
 const db = admin.database();
 
 // TODO: Use firebase functions:config:set to configure your googleapi object:
-// googleapi.client_id = Google API client ID, 
-// googleapi.client_secret = client secret, and 
+// googleapi.client_id = Google API client ID,
+// googleapi.client_secret = client secret, and
 // googleapi.sheet_id = Google Sheet id (long string in middle of sheet URL)
 const CONFIG_CLIENT_ID = functions.config().googleapi.client_id;
 const CONFIG_CLIENT_SECRET = functions.config().googleapi.client_secret;
@@ -54,8 +54,8 @@ exports.authgoogleapi = functions.https.onRequest((req, res) => {
   res.redirect(functionsOauthClient.generateAuthUrl({
     access_type: 'offline',
     scope: SCOPES,
-    prompt: 'consent'
-  }))
+    prompt: 'consent',
+  }));
 });
 
 // setup for OauthCallback
@@ -69,18 +69,19 @@ exports.oauthcallback = functions.https.onRequest((req, res) => {
   functionsOauthClient.getToken(code, (err, tokens) => {
     // Now tokens contains an access_token and an optional refresh_token. Save them.
     if (err) {
-      res.status(400).send(err);
-      return;
+      return res.status(400).send(err);
     }
-    db.ref(DB_TOKEN_PATH).set(tokens).then(
-        () => res.status(200).send('App successfully configured with new Credentials. ' +
-                                   'You can now close this page.'));
+    return db.ref(DB_TOKEN_PATH).set(tokens)
+        .then(() => {
+          return res.status(200).send('App successfully configured with new Credentials. '
+            + 'You can now close this page.');
+        });
   });
 });
 
 // trigger function to write to Sheet when new data comes in on CONFIG_DATA_PATH
 exports.appendrecordtospreadsheet = functions.database.ref(`${CONFIG_DATA_PATH}/{ITEM}`).onWrite(
-  event => {
+  (event) => {
     const newRecord = event.data.current.val();
     return appendPromise({
       spreadsheetId: CONFIG_SHEET_ID,
@@ -88,26 +89,27 @@ exports.appendrecordtospreadsheet = functions.database.ref(`${CONFIG_DATA_PATH}/
       valueInputOption: 'USER_ENTERED',
       insertDataOption: 'INSERT_ROWS',
       resource: {
-        values: [[newRecord.firstColumn, newRecord.secondColumn, newRecord.thirdColumn]]
-      }
+        values: [[newRecord.firstColumn, newRecord.secondColumn, newRecord.thirdColumn]],
+      },
     });
-});
+  }
+);
 
 // accepts an append request, returns a Promise to append it, enriching it with auth
 function appendPromise(requestWithoutAuth) {
   return new Promise((resolve, reject) => {
-    getAuthorizedClient().then(client => {
+    return getAuthorizedClient().then((client) => {
       const sheets = google.sheets('v4');
       const request = requestWithoutAuth;
       request.auth = client;
-      sheets.spreadsheets.values.append(request, (err, response) => {
+      return sheets.spreadsheets.values.append(request, (err, response) => {
         if (err) {
           console.log(`The API returned an error: ${err}`);
-          return reject();
+          return reject(err);
         }
         return resolve(response);
       });
-    }).catch(() => reject());
+    });
   });
 }
 
@@ -116,11 +118,11 @@ function getAuthorizedClient() {
   if (oauthTokens) {
     return Promise.resolve(functionsOauthClient);
   }
-  return db.ref(DB_TOKEN_PATH).once('value').then(snapshot => {
+  return db.ref(DB_TOKEN_PATH).once('value').then((snapshot) => {
     oauthTokens = snapshot.val();
     functionsOauthClient.setCredentials(oauthTokens);
     return functionsOauthClient;
-  })
+  });
 }
 
 // HTTPS function to write new data to CONFIG_DATA_PATH, for testing
@@ -132,7 +134,7 @@ exports.testsheetwrite = functions.https.onRequest((req, res) => {
   return db.ref(`${CONFIG_DATA_PATH}/${ID}`).set({
     firstColumn: random1,
     secondColumn: random2,
-    thirdColumn: random3
+    thirdColumn: random3,
   }).then(() => res.status(200).send(
     `Wrote ${random1}, ${random2}, ${random3} to DB, trigger should now update Sheet.`));
 });
diff --git a/image-maker/functions/.eslintrc.json b/image-maker/functions/.eslintrc.json
new file mode 100644
index 0000000000..eb4c93169b
--- /dev/null
+++ b/image-maker/functions/.eslintrc.json
@@ -0,0 +1,125 @@
+{
+  "parserOptions": {
+    // Required for certain syntax usages
+    "ecmaVersion": 6
+  },
+  "plugins": [
+    "promise"
+  ],
+  "extends": "eslint:recommended",
+  "rules": {
+    // Removed rule "disallow the use of console" from recommended eslint rules
+    "no-console": "off",
+
+    // Removed rule "disallow multiple spaces in regular expressions" from recommended eslint rules
+    "no-regex-spaces": "off",
+
+    // Removed rule "disallow the use of debugger" from recommended eslint rules
+    "no-debugger": "off",
+
+    // Removed rule "disallow unused variables" from recommended eslint rules
+    "no-unused-vars": "off",
+
+    // Removed rule "disallow mixed spaces and tabs for indentation" from recommended eslint rules
+    "no-mixed-spaces-and-tabs": "off",
+
+    // Removed rule "disallow the use of undeclared variables unless mentioned in /*global */ comments" from recommended eslint rules
+    "no-undef": "off",
+
+    // Warn against template literal placeholder syntax in regular strings
+    "no-template-curly-in-string": 1,
+
+    // Warn if return statements do not either always or never specify values
+    "consistent-return": 1,
+
+    // Warn if no return statements in callbacks of array methods
+    "array-callback-return": 1,
+
+    // Requre the use of === and !==
+    "eqeqeq": 2,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    // Disallow the use of alert, confirm, and prompt
+    "no-alert": 2,
+
+    // Disallow the use of arguments.caller or arguments.callee
+    "no-caller": 2,
+
+    // Disallow null comparisons without type-checking operators
+    "no-eq-null": 2,
+
+    // Disallow the use of eval()
+    "no-eval": 2,
+
+    // Warn against extending native types
+    "no-extend-native": 1,
+
+    // Warn against unnecessary calls to .bind()
+    "no-extra-bind": 1,
+
+    // Warn against unnecessary labels    
+    "no-extra-label": 1,
+
+    // Disallow leading or trailing decimal points in numeric literals
+    "no-floating-decimal": 2,
+
+    // Warn against shorthand type conversions
+    "no-implicit-coercion": 1,
+
+    // Warn against function declarations and expressions inside loop statements
+    "no-loop-func": 1,
+
+    // Disallow new operators with the Function object
+    "no-new-func": 2,
+
+    // Warn against new operators with the String, Number, and Boolean objects
+    "no-new-wrappers": 1,
+
+    // Disallow throwing literals as exceptions
+    "no-throw-literal": 2,
+
+    // Require using Error objects as Promise rejection reasons
+    "prefer-promise-reject-errors": 2,
+
+    // Enforce “for” loop update clause moving the counter in the right direction
+    "for-direction": 2,
+
+    // Enforce return statements in getters
+    "getter-return": 2,
+
+    // Disallow await inside of loops
+    "no-await-in-loop": 2,
+
+    // Disallow comparing against -0
+    "no-compare-neg-zero": 2,
+
+    // Warn against catch clause parameters from shadowing variables in the outer scope
+    "no-catch-shadow": 1,
+
+    // Disallow identifiers from shadowing restricted names
+    "no-shadow-restricted-names": 2,
+
+    // Enforce return statements in callbacks of array methods
+    "callback-return": 2,
+
+    // Require error handling in callbacks
+    "handle-callback-err": 2,
+
+    // Warn against string concatenation with __dirname and __filename
+    "no-path-concat": 1,
+
+    // Prefer using arrow functions for callbacks
+    "prefer-arrow-callback": 1,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    //Enforces the use of catch() on un-returned promises
+    "promise/catch-or-return": 2,
+
+    // Warn against nested then() or catch() statements
+    "promise/no-nesting": 1
+  }
+}
diff --git a/image-maker/functions/index.js b/image-maker/functions/index.js
index 0f8417a3b0..ce66301fc4 100644
--- a/image-maker/functions/index.js
+++ b/image-maker/functions/index.js
@@ -27,27 +27,27 @@ app.get('/api/ray', (req, res) => {
   const tracers = JSON.parse(req.query.tracers);
   if (!_.isArray(tracers) ||
     !_.every(tracers, (depth) => typeof depth === 'number')) {
-    //invalid format
+    // invalid format
     res.status(422);
     res.end();
   }
   const canvas = new Canvas(243 * tracers.length, 243);
   const ctx = canvas.getContext('2d');
-  for (var i=0; i<tracers.length; i++) {
-    ray(Math.round(27/tracers[i]), 81, ctx, { x: 243, y: 0 });
+  for (let i=0; i<tracers.length; i++) {
+    ray(Math.round(27/tracers[i]), 81, ctx, {x: 243, y: 0});
   }
   res.set('Cache-Control', 'public, max-age=60, s-maxage=31536000');
-  res.writeHead(200, { 'Content-Type': 'image/png' })
+  res.writeHead(200, {'Content-Type': 'image/png'});
   canvas.pngStream().pipe(res);
 });
 
 app.get('/api/clock', (req, res) => {
   const colorOpts = req.query;
-  const canvas = new Canvas(320, 320)
-  const ctx = canvas.getContext('2d')
+  const canvas = new Canvas(320, 320);
+  const ctx = canvas.getContext('2d');
   clock(ctx, colorOpts);
   res.set('Cache-Control', 'public, max-age=60, s-maxage=31536000');
-  res.writeHead(200, { 'Content-Type': 'image/png' })
+  res.writeHead(200, {'Content-Type': 'image/png'});
   canvas.pngStream().pipe(res);
 });
 
@@ -55,15 +55,15 @@ app.get('/api/spark', (req, res) => {
   const dataSeries = JSON.parse(req.query.series);
   const colorOpts = req.query.colorOpts || {};
   if (!_.isArray(dataSeries) || !_.every(dataSeries, (num) => typeof num === 'number')) {
-    //invalid format
+    // invalid format
     res.status(422);
     res.end();
   }
   const canvas = new Canvas(320, 100);
-  var ctx = canvas.getContext('2d');
+  let ctx = canvas.getContext('2d');
   spark(ctx, dataSeries, colorOpts);
   res.set('Cache-Control', 'public, max-age=60, s-maxage=31536000');
-  res.writeHead(200, { 'Content-Type': 'image/png' })
+  res.writeHead(200, {'Content-Type': 'image/png'});
   canvas.pngStream().pipe(res);
 });
 
diff --git a/image-sharp/functions/.eslintrc.json b/image-sharp/functions/.eslintrc.json
new file mode 100644
index 0000000000..eb4c93169b
--- /dev/null
+++ b/image-sharp/functions/.eslintrc.json
@@ -0,0 +1,125 @@
+{
+  "parserOptions": {
+    // Required for certain syntax usages
+    "ecmaVersion": 6
+  },
+  "plugins": [
+    "promise"
+  ],
+  "extends": "eslint:recommended",
+  "rules": {
+    // Removed rule "disallow the use of console" from recommended eslint rules
+    "no-console": "off",
+
+    // Removed rule "disallow multiple spaces in regular expressions" from recommended eslint rules
+    "no-regex-spaces": "off",
+
+    // Removed rule "disallow the use of debugger" from recommended eslint rules
+    "no-debugger": "off",
+
+    // Removed rule "disallow unused variables" from recommended eslint rules
+    "no-unused-vars": "off",
+
+    // Removed rule "disallow mixed spaces and tabs for indentation" from recommended eslint rules
+    "no-mixed-spaces-and-tabs": "off",
+
+    // Removed rule "disallow the use of undeclared variables unless mentioned in /*global */ comments" from recommended eslint rules
+    "no-undef": "off",
+
+    // Warn against template literal placeholder syntax in regular strings
+    "no-template-curly-in-string": 1,
+
+    // Warn if return statements do not either always or never specify values
+    "consistent-return": 1,
+
+    // Warn if no return statements in callbacks of array methods
+    "array-callback-return": 1,
+
+    // Requre the use of === and !==
+    "eqeqeq": 2,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    // Disallow the use of alert, confirm, and prompt
+    "no-alert": 2,
+
+    // Disallow the use of arguments.caller or arguments.callee
+    "no-caller": 2,
+
+    // Disallow null comparisons without type-checking operators
+    "no-eq-null": 2,
+
+    // Disallow the use of eval()
+    "no-eval": 2,
+
+    // Warn against extending native types
+    "no-extend-native": 1,
+
+    // Warn against unnecessary calls to .bind()
+    "no-extra-bind": 1,
+
+    // Warn against unnecessary labels    
+    "no-extra-label": 1,
+
+    // Disallow leading or trailing decimal points in numeric literals
+    "no-floating-decimal": 2,
+
+    // Warn against shorthand type conversions
+    "no-implicit-coercion": 1,
+
+    // Warn against function declarations and expressions inside loop statements
+    "no-loop-func": 1,
+
+    // Disallow new operators with the Function object
+    "no-new-func": 2,
+
+    // Warn against new operators with the String, Number, and Boolean objects
+    "no-new-wrappers": 1,
+
+    // Disallow throwing literals as exceptions
+    "no-throw-literal": 2,
+
+    // Require using Error objects as Promise rejection reasons
+    "prefer-promise-reject-errors": 2,
+
+    // Enforce “for” loop update clause moving the counter in the right direction
+    "for-direction": 2,
+
+    // Enforce return statements in getters
+    "getter-return": 2,
+
+    // Disallow await inside of loops
+    "no-await-in-loop": 2,
+
+    // Disallow comparing against -0
+    "no-compare-neg-zero": 2,
+
+    // Warn against catch clause parameters from shadowing variables in the outer scope
+    "no-catch-shadow": 1,
+
+    // Disallow identifiers from shadowing restricted names
+    "no-shadow-restricted-names": 2,
+
+    // Enforce return statements in callbacks of array methods
+    "callback-return": 2,
+
+    // Require error handling in callbacks
+    "handle-callback-err": 2,
+
+    // Warn against string concatenation with __dirname and __filename
+    "no-path-concat": 1,
+
+    // Prefer using arrow functions for callbacks
+    "prefer-arrow-callback": 1,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    //Enforces the use of catch() on un-returned promises
+    "promise/catch-or-return": 2,
+
+    // Warn against nested then() or catch() statements
+    "promise/no-nesting": 1
+  }
+}
diff --git a/image-sharp/functions/index.js b/image-sharp/functions/index.js
index 4986ef7ea8..c56130001e 100644
--- a/image-sharp/functions/index.js
+++ b/image-sharp/functions/index.js
@@ -27,7 +27,7 @@ const THUMB_MAX_HEIGHT = 200;
  * When an image is uploaded in the Storage bucket We generate a thumbnail automatically using
  * Sharp.
  */
-exports.generateThumbnail = functions.storage.object().onChange(event => {
+exports.generateThumbnail = functions.storage.object().onChange((event) => {
   const object = event.data; // The Storage object.
 
   const fileBucket = object.bucket; // The Storage bucket that contains the file.
@@ -39,7 +39,7 @@ exports.generateThumbnail = functions.storage.object().onChange(event => {
   // Exit if this is triggered on a file that is not an image.
   if (!contentType.startsWith('image/')) {
     console.log('This is not an image.');
-    return;
+    return null;
   }
 
   // Get the file name.
@@ -47,27 +47,27 @@ exports.generateThumbnail = functions.storage.object().onChange(event => {
   // Exit if the image is already a thumbnail.
   if (fileName.startsWith('thumb_')) {
     console.log('Already a Thumbnail.');
-    return;
+    return null;
   }
 
   // Exit if this is a move or deletion event.
   if (resourceState === 'not_exists') {
     console.log('This is a deletion event.');
-    return;
+    return null;
   }
 
   // Exit if file exists but is not new and is only being triggered
   // because of a metadata change.
   if (resourceState === 'exists' && metageneration > 1) {
     console.log('This is a metadata change event.');
-    return;
+    return null;
   }
 
   // Download file from bucket.
   const bucket = gcs.bucket(fileBucket);
 
   const metadata = {
-    contentType: contentType
+    contentType: contentType,
   };
   // We add a 'thumb_' prefix to thumbnails file name. That's where we'll upload the thumbnail.
   const thumbFileName = `thumb_${fileName}`;
@@ -86,7 +86,8 @@ exports.generateThumbnail = functions.storage.object().onChange(event => {
 
   const streamAsPromise = new Promise((resolve, reject) =>
     thumbnailUploadStream.on('finish', resolve).on('error', reject));
+
   return streamAsPromise.then(() => {
-    console.log('Thumbnail created successfully');
+    return console.log('Thumbnail created successfully');
   });
 });
diff --git a/instagram-auth/functions/.eslintrc.json b/instagram-auth/functions/.eslintrc.json
new file mode 100644
index 0000000000..eb4c93169b
--- /dev/null
+++ b/instagram-auth/functions/.eslintrc.json
@@ -0,0 +1,125 @@
+{
+  "parserOptions": {
+    // Required for certain syntax usages
+    "ecmaVersion": 6
+  },
+  "plugins": [
+    "promise"
+  ],
+  "extends": "eslint:recommended",
+  "rules": {
+    // Removed rule "disallow the use of console" from recommended eslint rules
+    "no-console": "off",
+
+    // Removed rule "disallow multiple spaces in regular expressions" from recommended eslint rules
+    "no-regex-spaces": "off",
+
+    // Removed rule "disallow the use of debugger" from recommended eslint rules
+    "no-debugger": "off",
+
+    // Removed rule "disallow unused variables" from recommended eslint rules
+    "no-unused-vars": "off",
+
+    // Removed rule "disallow mixed spaces and tabs for indentation" from recommended eslint rules
+    "no-mixed-spaces-and-tabs": "off",
+
+    // Removed rule "disallow the use of undeclared variables unless mentioned in /*global */ comments" from recommended eslint rules
+    "no-undef": "off",
+
+    // Warn against template literal placeholder syntax in regular strings
+    "no-template-curly-in-string": 1,
+
+    // Warn if return statements do not either always or never specify values
+    "consistent-return": 1,
+
+    // Warn if no return statements in callbacks of array methods
+    "array-callback-return": 1,
+
+    // Requre the use of === and !==
+    "eqeqeq": 2,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    // Disallow the use of alert, confirm, and prompt
+    "no-alert": 2,
+
+    // Disallow the use of arguments.caller or arguments.callee
+    "no-caller": 2,
+
+    // Disallow null comparisons without type-checking operators
+    "no-eq-null": 2,
+
+    // Disallow the use of eval()
+    "no-eval": 2,
+
+    // Warn against extending native types
+    "no-extend-native": 1,
+
+    // Warn against unnecessary calls to .bind()
+    "no-extra-bind": 1,
+
+    // Warn against unnecessary labels    
+    "no-extra-label": 1,
+
+    // Disallow leading or trailing decimal points in numeric literals
+    "no-floating-decimal": 2,
+
+    // Warn against shorthand type conversions
+    "no-implicit-coercion": 1,
+
+    // Warn against function declarations and expressions inside loop statements
+    "no-loop-func": 1,
+
+    // Disallow new operators with the Function object
+    "no-new-func": 2,
+
+    // Warn against new operators with the String, Number, and Boolean objects
+    "no-new-wrappers": 1,
+
+    // Disallow throwing literals as exceptions
+    "no-throw-literal": 2,
+
+    // Require using Error objects as Promise rejection reasons
+    "prefer-promise-reject-errors": 2,
+
+    // Enforce “for” loop update clause moving the counter in the right direction
+    "for-direction": 2,
+
+    // Enforce return statements in getters
+    "getter-return": 2,
+
+    // Disallow await inside of loops
+    "no-await-in-loop": 2,
+
+    // Disallow comparing against -0
+    "no-compare-neg-zero": 2,
+
+    // Warn against catch clause parameters from shadowing variables in the outer scope
+    "no-catch-shadow": 1,
+
+    // Disallow identifiers from shadowing restricted names
+    "no-shadow-restricted-names": 2,
+
+    // Enforce return statements in callbacks of array methods
+    "callback-return": 2,
+
+    // Require error handling in callbacks
+    "handle-callback-err": 2,
+
+    // Warn against string concatenation with __dirname and __filename
+    "no-path-concat": 1,
+
+    // Prefer using arrow functions for callbacks
+    "prefer-arrow-callback": 1,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    //Enforces the use of catch() on un-returned promises
+    "promise/catch-or-return": 2,
+
+    // Warn against nested then() or catch() statements
+    "promise/no-nesting": 1
+  }
+}
diff --git a/instagram-auth/functions/index.js b/instagram-auth/functions/index.js
index 612cd10c27..bde6faaf82 100644
--- a/instagram-auth/functions/index.js
+++ b/instagram-auth/functions/index.js
@@ -24,7 +24,7 @@ const admin = require('firebase-admin');
 const serviceAccount = require('./service-account.json');
 admin.initializeApp({
   credential: admin.credential.cert(serviceAccount),
-  databaseURL: `https://${process.env.GCLOUD_PROJECT}.firebaseio.com`
+  databaseURL: `https://${process.env.GCLOUD_PROJECT}.firebaseio.com`,
 });
 
 const OAUTH_REDIRECT_URI = `https://${process.env.GCLOUD_PROJECT}.firebaseapp.com/popup.html`;
@@ -39,12 +39,12 @@ function instagramOAuth2Client() {
   const credentials = {
     client: {
       id: functions.config().instagram.client_id,
-      secret: functions.config().instagram.client_secret
+      secret: functions.config().instagram.client_secret,
     },
     auth: {
       tokenHost: 'https://api.instagram.com',
-      tokenPath: '/oauth/access_token'
-    }
+      tokenPath: '/oauth/access_token',
+    },
   };
   return require('simple-oauth2').create(credentials);
 }
@@ -59,11 +59,15 @@ exports.redirect = functions.https.onRequest((req, res) => {
   cookieParser()(req, res, () => {
     const state = req.cookies.state || crypto.randomBytes(20).toString('hex');
     console.log('Setting verification state:', state);
-    res.cookie('state', state.toString(), {maxAge: 3600000, secure: true, httpOnly: true});
+    res.cookie('state', state.toString(), {
+      maxAge: 3600000,
+      secure: true,
+      httpOnly: true,
+    });
     const redirectUri = oauth2.authorizationCode.authorizeURL({
       redirect_uri: OAUTH_REDIRECT_URI,
       scope: OAUTH_SCOPES,
-      state: state
+      state: state,
     });
     console.log('Redirecting to:', redirectUri);
     res.redirect(redirectUri);
@@ -80,7 +84,7 @@ exports.token = functions.https.onRequest((req, res) => {
   const oauth2 = instagramOAuth2Client();
 
   try {
-    cookieParser()(req, res, () => {
+    return cookieParser()(req, res, () => {
       console.log('Received verification state:', req.cookies.state);
       console.log('Received state:', req.query.state);
       if (!req.cookies.state) {
@@ -91,25 +95,29 @@ exports.token = functions.https.onRequest((req, res) => {
       console.log('Received auth code:', req.query.code);
       oauth2.authorizationCode.getToken({
         code: req.query.code,
-        redirect_uri: OAUTH_REDIRECT_URI
-      }).then(results => {
-        console.log('Auth code exchange result received:', results);
+        redirect_uri: OAUTH_REDIRECT_URI,
+      });
+    }).then((results) => {
+      console.log('Auth code exchange result received:', results);
 
-        // We have an Instagram access token and the user identity now.
-        const accessToken = results.access_token;
-        const instagramUserID = results.user.id;
-        const profilePic = results.user.profile_picture;
-        const userName = results.user.full_name;
+      // We have an Instagram access token and the user identity now.
+      const accessToken = results.access_token;
+      const instagramUserID = results.user.id;
+      const profilePic = results.user.profile_picture;
+      const userName = results.user.full_name;
 
-        // Create a Firebase account and get the Custom Auth Token.
-        createFirebaseAccount(instagramUserID, userName, profilePic, accessToken).then(firebaseToken => {
-          // Serve an HTML page that signs the user in and updates the user profile.
-          res.jsonp({token: firebaseToken});
-        });
+      // Create a Firebase account and get the Custom Auth Token.
+      return createFirebaseAccount(instagramUserID, userName, profilePic, accessToken);
+    }).then((firebaseToken) => {
+      // Serve an HTML page that signs the user in and updates the user profile.
+      return res.jsonp({
+        token: firebaseToken,
       });
     });
   } catch (error) {
-    return res.jsonp({error: error.toString});
+    return res.jsonp({
+      error: error.toString,
+    });
   }
 });
 
@@ -126,19 +134,18 @@ function createFirebaseAccount(instagramID, displayName, photoURL, accessToken)
 
   // Save the access token tot he Firebase Realtime Database.
   const databaseTask = admin.database().ref(`/instagramAccessToken/${uid}`)
-      .set(accessToken);
-
+    .set(accessToken);
   // Create or update the user account.
   const userCreationTask = admin.auth().updateUser(uid, {
     displayName: displayName,
-    photoURL: photoURL
-  }).catch(error => {
+    photoURL: photoURL,
+  }).catch((error) => {
     // If user does not exists we create it.
     if (error.code === 'auth/user-not-found') {
       return admin.auth().createUser({
         uid: uid,
         displayName: displayName,
-        photoURL: photoURL
+        photoURL: photoURL,
       });
     }
     throw error;
@@ -147,9 +154,9 @@ function createFirebaseAccount(instagramID, displayName, photoURL, accessToken)
   // Wait for all async task to complete then generate and return a custom auth token.
   return Promise.all([userCreationTask, databaseTask]).then(() => {
     // Create a Firebase custom auth token.
-    return admin.auth().createCustomToken(uid).then((token) => {
-      console.log('Created Custom token for UID "', uid, '" Token:', token);
-      return token;
-    });
+    return admin.auth().createCustomToken(uid);
+  }).then((token) => {
+    console.log('Created Custom token for UID "', uid, '" Token:', token);
+    return token;
   });
 }
diff --git a/isomorphic-react-app/functions/.eslintrc.json b/isomorphic-react-app/functions/.eslintrc.json
new file mode 100644
index 0000000000..eb4c93169b
--- /dev/null
+++ b/isomorphic-react-app/functions/.eslintrc.json
@@ -0,0 +1,125 @@
+{
+  "parserOptions": {
+    // Required for certain syntax usages
+    "ecmaVersion": 6
+  },
+  "plugins": [
+    "promise"
+  ],
+  "extends": "eslint:recommended",
+  "rules": {
+    // Removed rule "disallow the use of console" from recommended eslint rules
+    "no-console": "off",
+
+    // Removed rule "disallow multiple spaces in regular expressions" from recommended eslint rules
+    "no-regex-spaces": "off",
+
+    // Removed rule "disallow the use of debugger" from recommended eslint rules
+    "no-debugger": "off",
+
+    // Removed rule "disallow unused variables" from recommended eslint rules
+    "no-unused-vars": "off",
+
+    // Removed rule "disallow mixed spaces and tabs for indentation" from recommended eslint rules
+    "no-mixed-spaces-and-tabs": "off",
+
+    // Removed rule "disallow the use of undeclared variables unless mentioned in /*global */ comments" from recommended eslint rules
+    "no-undef": "off",
+
+    // Warn against template literal placeholder syntax in regular strings
+    "no-template-curly-in-string": 1,
+
+    // Warn if return statements do not either always or never specify values
+    "consistent-return": 1,
+
+    // Warn if no return statements in callbacks of array methods
+    "array-callback-return": 1,
+
+    // Requre the use of === and !==
+    "eqeqeq": 2,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    // Disallow the use of alert, confirm, and prompt
+    "no-alert": 2,
+
+    // Disallow the use of arguments.caller or arguments.callee
+    "no-caller": 2,
+
+    // Disallow null comparisons without type-checking operators
+    "no-eq-null": 2,
+
+    // Disallow the use of eval()
+    "no-eval": 2,
+
+    // Warn against extending native types
+    "no-extend-native": 1,
+
+    // Warn against unnecessary calls to .bind()
+    "no-extra-bind": 1,
+
+    // Warn against unnecessary labels    
+    "no-extra-label": 1,
+
+    // Disallow leading or trailing decimal points in numeric literals
+    "no-floating-decimal": 2,
+
+    // Warn against shorthand type conversions
+    "no-implicit-coercion": 1,
+
+    // Warn against function declarations and expressions inside loop statements
+    "no-loop-func": 1,
+
+    // Disallow new operators with the Function object
+    "no-new-func": 2,
+
+    // Warn against new operators with the String, Number, and Boolean objects
+    "no-new-wrappers": 1,
+
+    // Disallow throwing literals as exceptions
+    "no-throw-literal": 2,
+
+    // Require using Error objects as Promise rejection reasons
+    "prefer-promise-reject-errors": 2,
+
+    // Enforce “for” loop update clause moving the counter in the right direction
+    "for-direction": 2,
+
+    // Enforce return statements in getters
+    "getter-return": 2,
+
+    // Disallow await inside of loops
+    "no-await-in-loop": 2,
+
+    // Disallow comparing against -0
+    "no-compare-neg-zero": 2,
+
+    // Warn against catch clause parameters from shadowing variables in the outer scope
+    "no-catch-shadow": 1,
+
+    // Disallow identifiers from shadowing restricted names
+    "no-shadow-restricted-names": 2,
+
+    // Enforce return statements in callbacks of array methods
+    "callback-return": 2,
+
+    // Require error handling in callbacks
+    "handle-callback-err": 2,
+
+    // Warn against string concatenation with __dirname and __filename
+    "no-path-concat": 1,
+
+    // Prefer using arrow functions for callbacks
+    "prefer-arrow-callback": 1,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    //Enforces the use of catch() on un-returned promises
+    "promise/catch-or-return": 2,
+
+    // Warn against nested then() or catch() statements
+    "promise/no-nesting": 1
+  }
+}
diff --git a/isomorphic-react-app/functions/index.js b/isomorphic-react-app/functions/index.js
index 885ddef30c..0af375e89f 100644
--- a/isomorphic-react-app/functions/index.js
+++ b/isomorphic-react-app/functions/index.js
@@ -32,13 +32,13 @@ database.initializeApp(appConfig);
 // Helper function to get the markup from React, inject the initial state, and
 // send the server-side markup to the client
 const renderApplication = (url, res, initialState) => {
-  const html = ReactDOMServer.renderToString(ServerApp({url: url, context: {}, initialState, appConfig}));
-  const templatedHtml = template({body: html, initialState: JSON.stringify(initialState)});
-  res.send(templatedHtml);
+    const html = ReactDOMServer.renderToString(ServerApp({url: url, context: {}, initialState, appConfig}));
+    const templatedHtml = template({body: html, initialState: JSON.stringify(initialState)});
+    res.send(templatedHtml);
 };
 
-app.get('/favicon.ico', function(req, res) {
-  res.send(204);
+app.get('/favicon.ico', (req, res) => {
+  return res.send(204);
 });
 
 app.get('/:userId?', (req, res) => {
@@ -46,13 +46,13 @@ app.get('/:userId?', (req, res) => {
   if (req.params.userId) {
     // client is requesting user-details page with userId
     // load the data for that employee and its direct reports
-    database.getEmployeeById(req.params.userId).then(resp => {
-      renderApplication(req.url, res, resp);
+    return database.getEmployeeById(req.params.userId).then((resp) => {
+      return renderApplication(req.url, res, resp);
     });
   } else {
     // index page. load data for all employees
-    database.getAllEmployees().then(resp => {
-      renderApplication(req.url, res, resp);
+    return database.getAllEmployees().then((resp) => {
+      return renderApplication(req.url, res, resp);
     });
   }
 });
diff --git a/lastmodified-tracking/functions/.eslintrc.json b/lastmodified-tracking/functions/.eslintrc.json
new file mode 100644
index 0000000000..eb4c93169b
--- /dev/null
+++ b/lastmodified-tracking/functions/.eslintrc.json
@@ -0,0 +1,125 @@
+{
+  "parserOptions": {
+    // Required for certain syntax usages
+    "ecmaVersion": 6
+  },
+  "plugins": [
+    "promise"
+  ],
+  "extends": "eslint:recommended",
+  "rules": {
+    // Removed rule "disallow the use of console" from recommended eslint rules
+    "no-console": "off",
+
+    // Removed rule "disallow multiple spaces in regular expressions" from recommended eslint rules
+    "no-regex-spaces": "off",
+
+    // Removed rule "disallow the use of debugger" from recommended eslint rules
+    "no-debugger": "off",
+
+    // Removed rule "disallow unused variables" from recommended eslint rules
+    "no-unused-vars": "off",
+
+    // Removed rule "disallow mixed spaces and tabs for indentation" from recommended eslint rules
+    "no-mixed-spaces-and-tabs": "off",
+
+    // Removed rule "disallow the use of undeclared variables unless mentioned in /*global */ comments" from recommended eslint rules
+    "no-undef": "off",
+
+    // Warn against template literal placeholder syntax in regular strings
+    "no-template-curly-in-string": 1,
+
+    // Warn if return statements do not either always or never specify values
+    "consistent-return": 1,
+
+    // Warn if no return statements in callbacks of array methods
+    "array-callback-return": 1,
+
+    // Requre the use of === and !==
+    "eqeqeq": 2,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    // Disallow the use of alert, confirm, and prompt
+    "no-alert": 2,
+
+    // Disallow the use of arguments.caller or arguments.callee
+    "no-caller": 2,
+
+    // Disallow null comparisons without type-checking operators
+    "no-eq-null": 2,
+
+    // Disallow the use of eval()
+    "no-eval": 2,
+
+    // Warn against extending native types
+    "no-extend-native": 1,
+
+    // Warn against unnecessary calls to .bind()
+    "no-extra-bind": 1,
+
+    // Warn against unnecessary labels    
+    "no-extra-label": 1,
+
+    // Disallow leading or trailing decimal points in numeric literals
+    "no-floating-decimal": 2,
+
+    // Warn against shorthand type conversions
+    "no-implicit-coercion": 1,
+
+    // Warn against function declarations and expressions inside loop statements
+    "no-loop-func": 1,
+
+    // Disallow new operators with the Function object
+    "no-new-func": 2,
+
+    // Warn against new operators with the String, Number, and Boolean objects
+    "no-new-wrappers": 1,
+
+    // Disallow throwing literals as exceptions
+    "no-throw-literal": 2,
+
+    // Require using Error objects as Promise rejection reasons
+    "prefer-promise-reject-errors": 2,
+
+    // Enforce “for” loop update clause moving the counter in the right direction
+    "for-direction": 2,
+
+    // Enforce return statements in getters
+    "getter-return": 2,
+
+    // Disallow await inside of loops
+    "no-await-in-loop": 2,
+
+    // Disallow comparing against -0
+    "no-compare-neg-zero": 2,
+
+    // Warn against catch clause parameters from shadowing variables in the outer scope
+    "no-catch-shadow": 1,
+
+    // Disallow identifiers from shadowing restricted names
+    "no-shadow-restricted-names": 2,
+
+    // Enforce return statements in callbacks of array methods
+    "callback-return": 2,
+
+    // Require error handling in callbacks
+    "handle-callback-err": 2,
+
+    // Warn against string concatenation with __dirname and __filename
+    "no-path-concat": 1,
+
+    // Prefer using arrow functions for callbacks
+    "prefer-arrow-callback": 1,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    //Enforces the use of catch() on un-returned promises
+    "promise/catch-or-return": 2,
+
+    // Warn against nested then() or catch() statements
+    "promise/no-nesting": 1
+  }
+}
diff --git a/lastmodified-tracking/functions/index.js b/lastmodified-tracking/functions/index.js
index 9a0aaac7c5..f53a02b42b 100644
--- a/lastmodified-tracking/functions/index.js
+++ b/lastmodified-tracking/functions/index.js
@@ -23,4 +23,4 @@ admin.initializeApp(functions.config().firebase);
  * This Function updates the `/lastmodified` with the timestamp of the last write to `/chat/$message`.
  */
 exports.touch = functions.database.ref('/chat/{message}').onWrite(
-    event => admin.database().ref('/lastmodified').set(event.timestamp));
+    (event) => admin.database().ref('/lastmodified').set(event.timestamp));
diff --git a/limit-children/functions/.eslintrc.json b/limit-children/functions/.eslintrc.json
new file mode 100644
index 0000000000..eb4c93169b
--- /dev/null
+++ b/limit-children/functions/.eslintrc.json
@@ -0,0 +1,125 @@
+{
+  "parserOptions": {
+    // Required for certain syntax usages
+    "ecmaVersion": 6
+  },
+  "plugins": [
+    "promise"
+  ],
+  "extends": "eslint:recommended",
+  "rules": {
+    // Removed rule "disallow the use of console" from recommended eslint rules
+    "no-console": "off",
+
+    // Removed rule "disallow multiple spaces in regular expressions" from recommended eslint rules
+    "no-regex-spaces": "off",
+
+    // Removed rule "disallow the use of debugger" from recommended eslint rules
+    "no-debugger": "off",
+
+    // Removed rule "disallow unused variables" from recommended eslint rules
+    "no-unused-vars": "off",
+
+    // Removed rule "disallow mixed spaces and tabs for indentation" from recommended eslint rules
+    "no-mixed-spaces-and-tabs": "off",
+
+    // Removed rule "disallow the use of undeclared variables unless mentioned in /*global */ comments" from recommended eslint rules
+    "no-undef": "off",
+
+    // Warn against template literal placeholder syntax in regular strings
+    "no-template-curly-in-string": 1,
+
+    // Warn if return statements do not either always or never specify values
+    "consistent-return": 1,
+
+    // Warn if no return statements in callbacks of array methods
+    "array-callback-return": 1,
+
+    // Requre the use of === and !==
+    "eqeqeq": 2,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    // Disallow the use of alert, confirm, and prompt
+    "no-alert": 2,
+
+    // Disallow the use of arguments.caller or arguments.callee
+    "no-caller": 2,
+
+    // Disallow null comparisons without type-checking operators
+    "no-eq-null": 2,
+
+    // Disallow the use of eval()
+    "no-eval": 2,
+
+    // Warn against extending native types
+    "no-extend-native": 1,
+
+    // Warn against unnecessary calls to .bind()
+    "no-extra-bind": 1,
+
+    // Warn against unnecessary labels    
+    "no-extra-label": 1,
+
+    // Disallow leading or trailing decimal points in numeric literals
+    "no-floating-decimal": 2,
+
+    // Warn against shorthand type conversions
+    "no-implicit-coercion": 1,
+
+    // Warn against function declarations and expressions inside loop statements
+    "no-loop-func": 1,
+
+    // Disallow new operators with the Function object
+    "no-new-func": 2,
+
+    // Warn against new operators with the String, Number, and Boolean objects
+    "no-new-wrappers": 1,
+
+    // Disallow throwing literals as exceptions
+    "no-throw-literal": 2,
+
+    // Require using Error objects as Promise rejection reasons
+    "prefer-promise-reject-errors": 2,
+
+    // Enforce “for” loop update clause moving the counter in the right direction
+    "for-direction": 2,
+
+    // Enforce return statements in getters
+    "getter-return": 2,
+
+    // Disallow await inside of loops
+    "no-await-in-loop": 2,
+
+    // Disallow comparing against -0
+    "no-compare-neg-zero": 2,
+
+    // Warn against catch clause parameters from shadowing variables in the outer scope
+    "no-catch-shadow": 1,
+
+    // Disallow identifiers from shadowing restricted names
+    "no-shadow-restricted-names": 2,
+
+    // Enforce return statements in callbacks of array methods
+    "callback-return": 2,
+
+    // Require error handling in callbacks
+    "handle-callback-err": 2,
+
+    // Warn against string concatenation with __dirname and __filename
+    "no-path-concat": 1,
+
+    // Prefer using arrow functions for callbacks
+    "prefer-arrow-callback": 1,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    //Enforces the use of catch() on un-returned promises
+    "promise/catch-or-return": 2,
+
+    // Warn against nested then() or catch() statements
+    "promise/no-nesting": 1
+  }
+}
diff --git a/limit-children/functions/index.js b/limit-children/functions/index.js
index 444265dc99..11e97b0a46 100644
--- a/limit-children/functions/index.js
+++ b/limit-children/functions/index.js
@@ -22,13 +22,13 @@ const MAX_LOG_COUNT = 5;
 
 // Removes siblings of the node that element that triggered the function if there are more than MAX_LOG_COUNT.
 // In this example we'll keep the max number of chat message history to MAX_LOG_COUNT.
-exports.truncate = functions.database.ref('/chat/{messageid}').onWrite(event => {
+exports.truncate = functions.database.ref('/chat/{messageid}').onWrite((event) => {
   const parentRef = event.data.ref.parent;
-  return parentRef.once('value').then(snapshot => {
+  return parentRef.once('value').then((snapshot) => {
     if (snapshot.numChildren() >= MAX_LOG_COUNT) {
       let childCount = 0;
       const updates = {};
-      snapshot.forEach(function(child) {
+      snapshot.forEach((child) => {
         if (++childCount <= snapshot.numChildren() - MAX_LOG_COUNT) {
           updates[child.key] = null;
         }
@@ -36,5 +36,6 @@ exports.truncate = functions.database.ref('/chat/{messageid}').onWrite(event =>
       // Update the parent. This effectively removes the extra children.
       return parentRef.update(updates);
     }
+    return null;
   });
 });
diff --git a/line-auth/functions/.eslintrc.json b/line-auth/functions/.eslintrc.json
new file mode 100644
index 0000000000..eb4c93169b
--- /dev/null
+++ b/line-auth/functions/.eslintrc.json
@@ -0,0 +1,125 @@
+{
+  "parserOptions": {
+    // Required for certain syntax usages
+    "ecmaVersion": 6
+  },
+  "plugins": [
+    "promise"
+  ],
+  "extends": "eslint:recommended",
+  "rules": {
+    // Removed rule "disallow the use of console" from recommended eslint rules
+    "no-console": "off",
+
+    // Removed rule "disallow multiple spaces in regular expressions" from recommended eslint rules
+    "no-regex-spaces": "off",
+
+    // Removed rule "disallow the use of debugger" from recommended eslint rules
+    "no-debugger": "off",
+
+    // Removed rule "disallow unused variables" from recommended eslint rules
+    "no-unused-vars": "off",
+
+    // Removed rule "disallow mixed spaces and tabs for indentation" from recommended eslint rules
+    "no-mixed-spaces-and-tabs": "off",
+
+    // Removed rule "disallow the use of undeclared variables unless mentioned in /*global */ comments" from recommended eslint rules
+    "no-undef": "off",
+
+    // Warn against template literal placeholder syntax in regular strings
+    "no-template-curly-in-string": 1,
+
+    // Warn if return statements do not either always or never specify values
+    "consistent-return": 1,
+
+    // Warn if no return statements in callbacks of array methods
+    "array-callback-return": 1,
+
+    // Requre the use of === and !==
+    "eqeqeq": 2,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    // Disallow the use of alert, confirm, and prompt
+    "no-alert": 2,
+
+    // Disallow the use of arguments.caller or arguments.callee
+    "no-caller": 2,
+
+    // Disallow null comparisons without type-checking operators
+    "no-eq-null": 2,
+
+    // Disallow the use of eval()
+    "no-eval": 2,
+
+    // Warn against extending native types
+    "no-extend-native": 1,
+
+    // Warn against unnecessary calls to .bind()
+    "no-extra-bind": 1,
+
+    // Warn against unnecessary labels    
+    "no-extra-label": 1,
+
+    // Disallow leading or trailing decimal points in numeric literals
+    "no-floating-decimal": 2,
+
+    // Warn against shorthand type conversions
+    "no-implicit-coercion": 1,
+
+    // Warn against function declarations and expressions inside loop statements
+    "no-loop-func": 1,
+
+    // Disallow new operators with the Function object
+    "no-new-func": 2,
+
+    // Warn against new operators with the String, Number, and Boolean objects
+    "no-new-wrappers": 1,
+
+    // Disallow throwing literals as exceptions
+    "no-throw-literal": 2,
+
+    // Require using Error objects as Promise rejection reasons
+    "prefer-promise-reject-errors": 2,
+
+    // Enforce “for” loop update clause moving the counter in the right direction
+    "for-direction": 2,
+
+    // Enforce return statements in getters
+    "getter-return": 2,
+
+    // Disallow await inside of loops
+    "no-await-in-loop": 2,
+
+    // Disallow comparing against -0
+    "no-compare-neg-zero": 2,
+
+    // Warn against catch clause parameters from shadowing variables in the outer scope
+    "no-catch-shadow": 1,
+
+    // Disallow identifiers from shadowing restricted names
+    "no-shadow-restricted-names": 2,
+
+    // Enforce return statements in callbacks of array methods
+    "callback-return": 2,
+
+    // Require error handling in callbacks
+    "handle-callback-err": 2,
+
+    // Warn against string concatenation with __dirname and __filename
+    "no-path-concat": 1,
+
+    // Prefer using arrow functions for callbacks
+    "prefer-arrow-callback": 1,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    //Enforces the use of catch() on un-returned promises
+    "promise/catch-or-return": 2,
+
+    // Warn against nested then() or catch() statements
+    "promise/no-nesting": 1
+  }
+}
diff --git a/line-auth/functions/index.js b/line-auth/functions/index.js
index 0ad331d3ed..0208efb514 100644
--- a/line-auth/functions/index.js
+++ b/line-auth/functions/index.js
@@ -32,15 +32,15 @@ function generateLineApiRequest(apiEndpoint, lineAccessToken) {
   return {
     url: apiEndpoint,
     headers: {
-      'Authorization': `Bearer ${lineAccessToken}`
+      'Authorization': `Bearer ${lineAccessToken}`,
     },
-    json: true
+    json: true,
   };
 }
 
 /**
  * Look up Firebase user based on LINE's mid. If the Firebase user does not exist,
- + fetch LINE profile and create a new Firebase user with it.
+ * fetch LINE profile and create a new Firebase user with it.
  *
  * @returns {Promise<UserRecord>} The Firebase user record in a promise.
  */
@@ -51,30 +51,30 @@ function getFirebaseUser(lineMid, lineAccessToken) {
   // LINE's get user profile API endpoint
   const getProfileOptions = generateLineApiRequest('https://api.line.me/v1/profile', lineAccessToken);
 
-  return admin.auth().getUser(firebaseUid).catch(error => {
+  return admin.auth().getUser(firebaseUid).catch((error) => {
     // If user does not exist, fetch LINE profile and create a Firebase new user with it
     if (error.code === 'auth/user-not-found') {
-      return rp(getProfileOptions).then(response => {
-        // Parse user profile from LINE's get user profile API response
-        const displayName = response.displayName;
-        const photoURL = response.pictureUrl;
-   
-        console.log('Create new Firebase user for LINE user mid = "', lineMid,'"');
-        // Create a new Firebase user with LINE profile and return it
-        return admin.auth().createUser({
-          uid: firebaseUid,
-          displayName: displayName,
-          photoURL: photoURL
-        });
-      });
+      return rp(getProfileOptions);
     }
     // If error other than auth/user-not-found occurred, fail the whole login process
-    throw error;
+    return Promise.reject(error);
+  }).then((response) => {
+    // Parse user profile from LINE's get user profile API response
+    const displayName = response.displayName;
+    const photoURL = response.pictureUrl;
+
+    console.log('Create new Firebase user for LINE user mid = "', lineMid, '"');
+    // Create a new Firebase user with LINE profile and return it
+    return admin.auth().createUser({
+      uid: firebaseUid,
+      displayName: displayName,
+      photoURL: photoURL,
+    });
   });
 }
 
 /**
- * Verify LINE access token and return a custom auth token allowing signing-in 
+ * Verify LINE access token and return a custom auth token allowing signing-in
  * the corresponding Firebase account.
  *
  * Here are the steps involved:
@@ -91,26 +91,25 @@ function verifyLineToken(lineAccessToken) {
 
   // STEP 1: Verify with LINE server that a LINE access token is valid
   return rp(verifyTokenOptions)
-    .then(response => {
+    .then((response) => {
       // Verify the token’s channelId match with my channelId to prevent spoof attack
       // <IMPORTANT> As LINE's Get user profiles API response doesn't include channelID,
       // you must not skip this step to make sure that the LINE access token is indeed
       // issued for your channel.
-      //TODO: consider !== here
-      if (response.channelId != functions.config().line.channelid) {
+      // TODO: consider !== here
+      if (response.channelId !== functions.config().line.channelid) {
         return Promise.reject(new Error('LINE channel ID mismatched'));
       }
 
       // STEP 2: Access token validation succeeded, so look up the corresponding Firebase user
       const lineMid = response.mid;
       return getFirebaseUser(lineMid, lineAccessToken);
-    })
-    .then(userRecord => {
+    }).then((userRecord) => {
       // STEP 3: Generate Firebase Custom Auth Token
-      return admin.auth().createCustomToken(userRecord.uid).then(token => {
-        console.log('Created Custom token for UID "', userRecord.uid, '" Token:', token);
-        return token;
-      });
+      return admin.auth().createCustomToken(userRecord.uid);
+    }).then((token) => {
+      console.log('Created Custom token for UID "', userRecord.uid, '" Token:', token);
+      return token;
     });
 }
 
@@ -118,7 +117,7 @@ function verifyLineToken(lineAccessToken) {
 exports.verifyToken = functions.https.onRequest((req, res) => {
   if (req.body.token === undefined) {
     const ret = {
-      error_message: 'Access Token not found'
+      error_message: 'Access Token not found',
     };
     return res.status(400).send(ret);
   }
@@ -126,18 +125,18 @@ exports.verifyToken = functions.https.onRequest((req, res) => {
   const reqToken = req.body.token;
 
   // Verify LINE access token with LINE server then generate Firebase Custom Auth token
-  verifyLineToken(reqToken)
-    .then(customAuthToken => {
+  return verifyLineToken(reqToken)
+    .then((customAuthToken) => {
       const ret = {
-        firebase_token: customAuthToken
+        firebase_token: customAuthToken,
       };
-      return res.status(200).send(ret);   
-    }).catch(err => {
+      return res.status(200).send(ret);
+    }).catch((err) => {
       // If LINE access token verification failed, return error response to client
       const ret = {
-        error_message: 'Authentication error: Cannot verify access token.'
+        error_message: 'Authentication error: Cannot verify access token.',
       };
       console.error('LINE token verification failed: ', err);
       return res.status(403).send(ret);
     });
-})
+});
diff --git a/linkedin-auth/functions/.eslintrc.json b/linkedin-auth/functions/.eslintrc.json
new file mode 100644
index 0000000000..eb4c93169b
--- /dev/null
+++ b/linkedin-auth/functions/.eslintrc.json
@@ -0,0 +1,125 @@
+{
+  "parserOptions": {
+    // Required for certain syntax usages
+    "ecmaVersion": 6
+  },
+  "plugins": [
+    "promise"
+  ],
+  "extends": "eslint:recommended",
+  "rules": {
+    // Removed rule "disallow the use of console" from recommended eslint rules
+    "no-console": "off",
+
+    // Removed rule "disallow multiple spaces in regular expressions" from recommended eslint rules
+    "no-regex-spaces": "off",
+
+    // Removed rule "disallow the use of debugger" from recommended eslint rules
+    "no-debugger": "off",
+
+    // Removed rule "disallow unused variables" from recommended eslint rules
+    "no-unused-vars": "off",
+
+    // Removed rule "disallow mixed spaces and tabs for indentation" from recommended eslint rules
+    "no-mixed-spaces-and-tabs": "off",
+
+    // Removed rule "disallow the use of undeclared variables unless mentioned in /*global */ comments" from recommended eslint rules
+    "no-undef": "off",
+
+    // Warn against template literal placeholder syntax in regular strings
+    "no-template-curly-in-string": 1,
+
+    // Warn if return statements do not either always or never specify values
+    "consistent-return": 1,
+
+    // Warn if no return statements in callbacks of array methods
+    "array-callback-return": 1,
+
+    // Requre the use of === and !==
+    "eqeqeq": 2,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    // Disallow the use of alert, confirm, and prompt
+    "no-alert": 2,
+
+    // Disallow the use of arguments.caller or arguments.callee
+    "no-caller": 2,
+
+    // Disallow null comparisons without type-checking operators
+    "no-eq-null": 2,
+
+    // Disallow the use of eval()
+    "no-eval": 2,
+
+    // Warn against extending native types
+    "no-extend-native": 1,
+
+    // Warn against unnecessary calls to .bind()
+    "no-extra-bind": 1,
+
+    // Warn against unnecessary labels    
+    "no-extra-label": 1,
+
+    // Disallow leading or trailing decimal points in numeric literals
+    "no-floating-decimal": 2,
+
+    // Warn against shorthand type conversions
+    "no-implicit-coercion": 1,
+
+    // Warn against function declarations and expressions inside loop statements
+    "no-loop-func": 1,
+
+    // Disallow new operators with the Function object
+    "no-new-func": 2,
+
+    // Warn against new operators with the String, Number, and Boolean objects
+    "no-new-wrappers": 1,
+
+    // Disallow throwing literals as exceptions
+    "no-throw-literal": 2,
+
+    // Require using Error objects as Promise rejection reasons
+    "prefer-promise-reject-errors": 2,
+
+    // Enforce “for” loop update clause moving the counter in the right direction
+    "for-direction": 2,
+
+    // Enforce return statements in getters
+    "getter-return": 2,
+
+    // Disallow await inside of loops
+    "no-await-in-loop": 2,
+
+    // Disallow comparing against -0
+    "no-compare-neg-zero": 2,
+
+    // Warn against catch clause parameters from shadowing variables in the outer scope
+    "no-catch-shadow": 1,
+
+    // Disallow identifiers from shadowing restricted names
+    "no-shadow-restricted-names": 2,
+
+    // Enforce return statements in callbacks of array methods
+    "callback-return": 2,
+
+    // Require error handling in callbacks
+    "handle-callback-err": 2,
+
+    // Warn against string concatenation with __dirname and __filename
+    "no-path-concat": 1,
+
+    // Prefer using arrow functions for callbacks
+    "prefer-arrow-callback": 1,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    //Enforces the use of catch() on un-returned promises
+    "promise/catch-or-return": 2,
+
+    // Warn against nested then() or catch() statements
+    "promise/no-nesting": 1
+  }
+}
diff --git a/linkedin-auth/functions/index.js b/linkedin-auth/functions/index.js
index 339d95b47f..0bf36ac0aa 100644
--- a/linkedin-auth/functions/index.js
+++ b/linkedin-auth/functions/index.js
@@ -24,7 +24,7 @@ const admin = require('firebase-admin');
 const serviceAccount = require('./service-account.json');
 admin.initializeApp({
   credential: admin.credential.cert(serviceAccount),
-  databaseURL: `https://${process.env.GCLOUD_PROJECT}.firebaseio.com`
+  databaseURL: `https://${process.env.GCLOUD_PROJECT}.firebaseio.com`,
 });
 
 const OAUTH_SCOPES = ['r_basicprofile', 'r_emailaddress'];
@@ -51,7 +51,11 @@ exports.redirect = functions.https.onRequest((req, res) => {
   cookieParser()(req, res, () => {
     const state = req.cookies.state || crypto.randomBytes(20).toString('hex');
     console.log('Setting verification state:', state);
-    res.cookie('state', state.toString(), {maxAge: 3600000, secure: true, httpOnly: true});
+    res.cookie('state', state.toString(), {
+      maxAge: 3600000,
+      secure: true,
+      httpOnly: true,
+    });
     Linkedin.auth.authorize(res, OAUTH_SCOPES, state.toString());
   });
 });
@@ -66,7 +70,7 @@ exports.token = functions.https.onRequest((req, res) => {
   const Linkedin = linkedInClient();
 
   try {
-    cookieParser()(req, res, () => {
+    return cookieParser()(req, res, () => {
       if (!req.cookies.state) {
         throw new Error('State cookie not set or expired. Maybe you took too long to authorize. Please try again.');
       }
@@ -94,16 +98,20 @@ exports.token = functions.https.onRequest((req, res) => {
           const email = userResults.emailAddress;
 
           // Create a Firebase account and get the Custom Auth Token.
-          createFirebaseAccount(linkedInUserID, userName, profilePic, email, accessToken).then(
-              firebaseToken => {
-                // Serve an HTML page that signs the user in and updates the user profile.
-                res.jsonp({token: firebaseToken});
+          return createFirebaseAccount(linkedInUserID, userName, profilePic, email, accessToken).then(
+            (firebaseToken) => {
+              // Serve an HTML page that signs the user in and updates the user profile.
+              return res.jsonp({
+                token: firebaseToken,
               });
+            });
         });
       });
     });
   } catch (error) {
-    return res.jsonp({error: error.toString});
+    return res.jsonp({
+      error: error.toString,
+    });
   }
 });
 
@@ -119,16 +127,15 @@ function createFirebaseAccount(linkedinID, displayName, photoURL, email, accessT
   const uid = `linkedin:${linkedinID}`;
 
   // Save the access token tot he Firebase Realtime Database.
-  const databaseTask = admin.database().ref(`/linkedInAccessToken/${uid}`)
-      .set(accessToken);
+  const databaseTask = admin.database().ref(`/linkedInAccessToken/${uid}`).set(accessToken);
 
   // Create or update the user account.
   const userCreationTask = admin.auth().updateUser(uid, {
     displayName: displayName,
     photoURL: photoURL,
     email: email,
-    emailVerified: true
-  }).catch(error => {
+    emailVerified: true,
+  }).catch((error) => {
     // If user does not exists we create it.
     if (error.code === 'auth/user-not-found') {
       return admin.auth().createUser({
@@ -136,7 +143,7 @@ function createFirebaseAccount(linkedinID, displayName, photoURL, email, accessT
         displayName: displayName,
         photoURL: photoURL,
         email: email,
-        emailVerified: true
+        emailVerified: true,
       });
     }
     throw error;
@@ -145,9 +152,9 @@ function createFirebaseAccount(linkedinID, displayName, photoURL, email, accessT
   // Wait for all async task to complete then generate and return a custom auth token.
   return Promise.all([userCreationTask, databaseTask]).then(() => {
     // Create a Firebase custom auth token.
-    return admin.auth().createCustomToken(uid).then((token) => {
-      console.log('Created Custom token for UID "', uid, '" Token:', token);
-      return token;
-    });
+    return admin.auth().createCustomToken(uid);
+  }).then((token) => {
+    console.log('Created Custom token for UID "', uid, '" Token:', token);
+    return token;
   });
 }
diff --git a/message-translation/functions/.eslintrc.json b/message-translation/functions/.eslintrc.json
new file mode 100644
index 0000000000..eb4c93169b
--- /dev/null
+++ b/message-translation/functions/.eslintrc.json
@@ -0,0 +1,125 @@
+{
+  "parserOptions": {
+    // Required for certain syntax usages
+    "ecmaVersion": 6
+  },
+  "plugins": [
+    "promise"
+  ],
+  "extends": "eslint:recommended",
+  "rules": {
+    // Removed rule "disallow the use of console" from recommended eslint rules
+    "no-console": "off",
+
+    // Removed rule "disallow multiple spaces in regular expressions" from recommended eslint rules
+    "no-regex-spaces": "off",
+
+    // Removed rule "disallow the use of debugger" from recommended eslint rules
+    "no-debugger": "off",
+
+    // Removed rule "disallow unused variables" from recommended eslint rules
+    "no-unused-vars": "off",
+
+    // Removed rule "disallow mixed spaces and tabs for indentation" from recommended eslint rules
+    "no-mixed-spaces-and-tabs": "off",
+
+    // Removed rule "disallow the use of undeclared variables unless mentioned in /*global */ comments" from recommended eslint rules
+    "no-undef": "off",
+
+    // Warn against template literal placeholder syntax in regular strings
+    "no-template-curly-in-string": 1,
+
+    // Warn if return statements do not either always or never specify values
+    "consistent-return": 1,
+
+    // Warn if no return statements in callbacks of array methods
+    "array-callback-return": 1,
+
+    // Requre the use of === and !==
+    "eqeqeq": 2,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    // Disallow the use of alert, confirm, and prompt
+    "no-alert": 2,
+
+    // Disallow the use of arguments.caller or arguments.callee
+    "no-caller": 2,
+
+    // Disallow null comparisons without type-checking operators
+    "no-eq-null": 2,
+
+    // Disallow the use of eval()
+    "no-eval": 2,
+
+    // Warn against extending native types
+    "no-extend-native": 1,
+
+    // Warn against unnecessary calls to .bind()
+    "no-extra-bind": 1,
+
+    // Warn against unnecessary labels    
+    "no-extra-label": 1,
+
+    // Disallow leading or trailing decimal points in numeric literals
+    "no-floating-decimal": 2,
+
+    // Warn against shorthand type conversions
+    "no-implicit-coercion": 1,
+
+    // Warn against function declarations and expressions inside loop statements
+    "no-loop-func": 1,
+
+    // Disallow new operators with the Function object
+    "no-new-func": 2,
+
+    // Warn against new operators with the String, Number, and Boolean objects
+    "no-new-wrappers": 1,
+
+    // Disallow throwing literals as exceptions
+    "no-throw-literal": 2,
+
+    // Require using Error objects as Promise rejection reasons
+    "prefer-promise-reject-errors": 2,
+
+    // Enforce “for” loop update clause moving the counter in the right direction
+    "for-direction": 2,
+
+    // Enforce return statements in getters
+    "getter-return": 2,
+
+    // Disallow await inside of loops
+    "no-await-in-loop": 2,
+
+    // Disallow comparing against -0
+    "no-compare-neg-zero": 2,
+
+    // Warn against catch clause parameters from shadowing variables in the outer scope
+    "no-catch-shadow": 1,
+
+    // Disallow identifiers from shadowing restricted names
+    "no-shadow-restricted-names": 2,
+
+    // Enforce return statements in callbacks of array methods
+    "callback-return": 2,
+
+    // Require error handling in callbacks
+    "handle-callback-err": 2,
+
+    // Warn against string concatenation with __dirname and __filename
+    "no-path-concat": 1,
+
+    // Prefer using arrow functions for callbacks
+    "prefer-arrow-callback": 1,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    //Enforces the use of catch() on un-returned promises
+    "promise/catch-or-return": 2,
+
+    // Warn against nested then() or catch() statements
+    "promise/no-nesting": 1
+  }
+}
diff --git a/message-translation/functions/index.js b/message-translation/functions/index.js
index 9be750b742..8c03dab8aa 100644
--- a/message-translation/functions/index.js
+++ b/message-translation/functions/index.js
@@ -24,14 +24,14 @@ const request = require('request-promise');
 const LANGUAGES = ['en', 'es', 'de', 'fr', 'sv', 'ga', 'it', 'jp'];
 
 // Translate an incoming message.
-exports.translate = functions.database.ref('/messages/{languageID}/{messageID}').onWrite(event => {
+exports.translate = functions.database.ref('/messages/{languageID}/{messageID}').onWrite((event) => {
   const snapshot = event.data;
   if (snapshot.val().translated) {
-    return;
+    return null;
   }
   const promises = [];
   for (let i = 0; i < LANGUAGES.length; i++) {
-    var language = LANGUAGES[i];
+    let language = LANGUAGES[i];
     if (language !== event.params.languageID) {
       promises.push(createTranslationPromise(event.params.languageID, language, snapshot));
     }
@@ -48,11 +48,11 @@ function createTranslationPromise(source, target, snapshot) {
   const key = snapshot.key;
   const message = snapshot.val().message;
   return request(createTranslateUrl(source, target, message), {resolveWithFullResponse: true}).then(
-      response => {
+      (response) => {
         if (response.statusCode === 200) {
           const data = JSON.parse(response.body).data;
           return admin.database().ref(`/messages/${target}/${key}`)
-              .set({message: data.translations[0].translatedText, translated: true});
+          .set({message: data.translations[0].translatedText, translated: true});
         }
         throw response.body;
       });
diff --git a/minimal-webhook/functions/.eslintrc.json b/minimal-webhook/functions/.eslintrc.json
new file mode 100644
index 0000000000..eb4c93169b
--- /dev/null
+++ b/minimal-webhook/functions/.eslintrc.json
@@ -0,0 +1,125 @@
+{
+  "parserOptions": {
+    // Required for certain syntax usages
+    "ecmaVersion": 6
+  },
+  "plugins": [
+    "promise"
+  ],
+  "extends": "eslint:recommended",
+  "rules": {
+    // Removed rule "disallow the use of console" from recommended eslint rules
+    "no-console": "off",
+
+    // Removed rule "disallow multiple spaces in regular expressions" from recommended eslint rules
+    "no-regex-spaces": "off",
+
+    // Removed rule "disallow the use of debugger" from recommended eslint rules
+    "no-debugger": "off",
+
+    // Removed rule "disallow unused variables" from recommended eslint rules
+    "no-unused-vars": "off",
+
+    // Removed rule "disallow mixed spaces and tabs for indentation" from recommended eslint rules
+    "no-mixed-spaces-and-tabs": "off",
+
+    // Removed rule "disallow the use of undeclared variables unless mentioned in /*global */ comments" from recommended eslint rules
+    "no-undef": "off",
+
+    // Warn against template literal placeholder syntax in regular strings
+    "no-template-curly-in-string": 1,
+
+    // Warn if return statements do not either always or never specify values
+    "consistent-return": 1,
+
+    // Warn if no return statements in callbacks of array methods
+    "array-callback-return": 1,
+
+    // Requre the use of === and !==
+    "eqeqeq": 2,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    // Disallow the use of alert, confirm, and prompt
+    "no-alert": 2,
+
+    // Disallow the use of arguments.caller or arguments.callee
+    "no-caller": 2,
+
+    // Disallow null comparisons without type-checking operators
+    "no-eq-null": 2,
+
+    // Disallow the use of eval()
+    "no-eval": 2,
+
+    // Warn against extending native types
+    "no-extend-native": 1,
+
+    // Warn against unnecessary calls to .bind()
+    "no-extra-bind": 1,
+
+    // Warn against unnecessary labels    
+    "no-extra-label": 1,
+
+    // Disallow leading or trailing decimal points in numeric literals
+    "no-floating-decimal": 2,
+
+    // Warn against shorthand type conversions
+    "no-implicit-coercion": 1,
+
+    // Warn against function declarations and expressions inside loop statements
+    "no-loop-func": 1,
+
+    // Disallow new operators with the Function object
+    "no-new-func": 2,
+
+    // Warn against new operators with the String, Number, and Boolean objects
+    "no-new-wrappers": 1,
+
+    // Disallow throwing literals as exceptions
+    "no-throw-literal": 2,
+
+    // Require using Error objects as Promise rejection reasons
+    "prefer-promise-reject-errors": 2,
+
+    // Enforce “for” loop update clause moving the counter in the right direction
+    "for-direction": 2,
+
+    // Enforce return statements in getters
+    "getter-return": 2,
+
+    // Disallow await inside of loops
+    "no-await-in-loop": 2,
+
+    // Disallow comparing against -0
+    "no-compare-neg-zero": 2,
+
+    // Warn against catch clause parameters from shadowing variables in the outer scope
+    "no-catch-shadow": 1,
+
+    // Disallow identifiers from shadowing restricted names
+    "no-shadow-restricted-names": 2,
+
+    // Enforce return statements in callbacks of array methods
+    "callback-return": 2,
+
+    // Require error handling in callbacks
+    "handle-callback-err": 2,
+
+    // Warn against string concatenation with __dirname and __filename
+    "no-path-concat": 1,
+
+    // Prefer using arrow functions for callbacks
+    "prefer-arrow-callback": 1,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    //Enforces the use of catch() on un-returned promises
+    "promise/catch-or-return": 2,
+
+    // Warn against nested then() or catch() statements
+    "promise/no-nesting": 1
+  }
+}
diff --git a/minimal-webhook/functions/index.js b/minimal-webhook/functions/index.js
index 844506833f..cd3f034391 100644
--- a/minimal-webhook/functions/index.js
+++ b/minimal-webhook/functions/index.js
@@ -25,17 +25,17 @@ const WEBHOOK_URL = 'http://requestb.in/1mqw97l1';
 
 // Reads the content of the node that triggered the function and sends it to the registered Webhook
 // URL.
-exports.webhook = functions.database.ref('/hooks/{hookId}').onWrite(event => {
+exports.webhook = functions.database.ref('/hooks/{hookId}').onWrite((event) => {
   return request({
     uri: WEBHOOK_URL,
     method: 'POST',
     json: true,
     body: event.data.val(),
-    resolveWithFullResponse: true
-  }).then(response => {
+    resolveWithFullResponse: true,
+  }).then((response) => {
     if (response.statusCode >= 400) {
       throw new Error(`HTTP Error: ${response.statusCode}`);
     }
-    console.log('SUCCESS! Posted', event.data.ref);
+    return console.log('SUCCESS! Posted', event.data.ref);
   });
 });
diff --git a/moderate-images/functions/.eslintrc.json b/moderate-images/functions/.eslintrc.json
new file mode 100644
index 0000000000..eb4c93169b
--- /dev/null
+++ b/moderate-images/functions/.eslintrc.json
@@ -0,0 +1,125 @@
+{
+  "parserOptions": {
+    // Required for certain syntax usages
+    "ecmaVersion": 6
+  },
+  "plugins": [
+    "promise"
+  ],
+  "extends": "eslint:recommended",
+  "rules": {
+    // Removed rule "disallow the use of console" from recommended eslint rules
+    "no-console": "off",
+
+    // Removed rule "disallow multiple spaces in regular expressions" from recommended eslint rules
+    "no-regex-spaces": "off",
+
+    // Removed rule "disallow the use of debugger" from recommended eslint rules
+    "no-debugger": "off",
+
+    // Removed rule "disallow unused variables" from recommended eslint rules
+    "no-unused-vars": "off",
+
+    // Removed rule "disallow mixed spaces and tabs for indentation" from recommended eslint rules
+    "no-mixed-spaces-and-tabs": "off",
+
+    // Removed rule "disallow the use of undeclared variables unless mentioned in /*global */ comments" from recommended eslint rules
+    "no-undef": "off",
+
+    // Warn against template literal placeholder syntax in regular strings
+    "no-template-curly-in-string": 1,
+
+    // Warn if return statements do not either always or never specify values
+    "consistent-return": 1,
+
+    // Warn if no return statements in callbacks of array methods
+    "array-callback-return": 1,
+
+    // Requre the use of === and !==
+    "eqeqeq": 2,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    // Disallow the use of alert, confirm, and prompt
+    "no-alert": 2,
+
+    // Disallow the use of arguments.caller or arguments.callee
+    "no-caller": 2,
+
+    // Disallow null comparisons without type-checking operators
+    "no-eq-null": 2,
+
+    // Disallow the use of eval()
+    "no-eval": 2,
+
+    // Warn against extending native types
+    "no-extend-native": 1,
+
+    // Warn against unnecessary calls to .bind()
+    "no-extra-bind": 1,
+
+    // Warn against unnecessary labels    
+    "no-extra-label": 1,
+
+    // Disallow leading or trailing decimal points in numeric literals
+    "no-floating-decimal": 2,
+
+    // Warn against shorthand type conversions
+    "no-implicit-coercion": 1,
+
+    // Warn against function declarations and expressions inside loop statements
+    "no-loop-func": 1,
+
+    // Disallow new operators with the Function object
+    "no-new-func": 2,
+
+    // Warn against new operators with the String, Number, and Boolean objects
+    "no-new-wrappers": 1,
+
+    // Disallow throwing literals as exceptions
+    "no-throw-literal": 2,
+
+    // Require using Error objects as Promise rejection reasons
+    "prefer-promise-reject-errors": 2,
+
+    // Enforce “for” loop update clause moving the counter in the right direction
+    "for-direction": 2,
+
+    // Enforce return statements in getters
+    "getter-return": 2,
+
+    // Disallow await inside of loops
+    "no-await-in-loop": 2,
+
+    // Disallow comparing against -0
+    "no-compare-neg-zero": 2,
+
+    // Warn against catch clause parameters from shadowing variables in the outer scope
+    "no-catch-shadow": 1,
+
+    // Disallow identifiers from shadowing restricted names
+    "no-shadow-restricted-names": 2,
+
+    // Enforce return statements in callbacks of array methods
+    "callback-return": 2,
+
+    // Require error handling in callbacks
+    "handle-callback-err": 2,
+
+    // Warn against string concatenation with __dirname and __filename
+    "no-path-concat": 1,
+
+    // Prefer using arrow functions for callbacks
+    "prefer-arrow-callback": 1,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    //Enforces the use of catch() on un-returned promises
+    "promise/catch-or-return": 2,
+
+    // Warn against nested then() or catch() statements
+    "promise/no-nesting": 1
+  }
+}
diff --git a/moderate-images/functions/index.js b/moderate-images/functions/index.js
index 21ad975dab..80927fa67e 100644
--- a/moderate-images/functions/index.js
+++ b/moderate-images/functions/index.js
@@ -28,7 +28,7 @@ const fs = require('fs');
  * When an image is uploaded we check if it is flagged as Adult or Violence by the Cloud Vision
  * API and if it is we blur it using ImageMagick.
  */
-exports.blurOffensiveImages = functions.storage.object().onChange(event => {
+exports.blurOffensiveImages = functions.storage.object().onChange((event) => {
   const object = event.data;
   const file = gcs.bucket(object.bucket).file(object.name);
 
@@ -38,13 +38,14 @@ exports.blurOffensiveImages = functions.storage.object().onChange(event => {
   }
 
   // Check the image content using the Cloud Vision API.
-  return vision.detectSafeSearch(file).then(data => {
+  return vision.detectSafeSearch(file).then((data) => {
     const safeSearch = data[0];
     console.log('SafeSearch results on image', safeSearch);
 
     if (safeSearch.adult || safeSearch.violence) {
       return blurImage(object.name, object.bucket, object.metadata);
     }
+    return null;
   });
 });
 
@@ -70,11 +71,11 @@ function blurImage(filePath, bucketName, metadata) {
     // Uploading the Blurred image.
     return bucket.upload(tempLocalFile, {
       destination: filePath,
-      metadata: {metadata: metadata} // Keeping custom metadata.
+      metadata: {metadata: metadata}, // Keeping custom metadata.
     });
   }).then(() => {
     console.log('Blurred image uploaded to Storage at', filePath);
     fs.unlinkSync(tempLocalFile);
-    console.log('Deleted local file', filePath);
+    return console.log('Deleted local file', filePath);
   });
 }
diff --git a/nextjs-with-firebase-hosting/src/functions/.eslintrc.json b/nextjs-with-firebase-hosting/src/functions/.eslintrc.json
new file mode 100644
index 0000000000..eb4c93169b
--- /dev/null
+++ b/nextjs-with-firebase-hosting/src/functions/.eslintrc.json
@@ -0,0 +1,125 @@
+{
+  "parserOptions": {
+    // Required for certain syntax usages
+    "ecmaVersion": 6
+  },
+  "plugins": [
+    "promise"
+  ],
+  "extends": "eslint:recommended",
+  "rules": {
+    // Removed rule "disallow the use of console" from recommended eslint rules
+    "no-console": "off",
+
+    // Removed rule "disallow multiple spaces in regular expressions" from recommended eslint rules
+    "no-regex-spaces": "off",
+
+    // Removed rule "disallow the use of debugger" from recommended eslint rules
+    "no-debugger": "off",
+
+    // Removed rule "disallow unused variables" from recommended eslint rules
+    "no-unused-vars": "off",
+
+    // Removed rule "disallow mixed spaces and tabs for indentation" from recommended eslint rules
+    "no-mixed-spaces-and-tabs": "off",
+
+    // Removed rule "disallow the use of undeclared variables unless mentioned in /*global */ comments" from recommended eslint rules
+    "no-undef": "off",
+
+    // Warn against template literal placeholder syntax in regular strings
+    "no-template-curly-in-string": 1,
+
+    // Warn if return statements do not either always or never specify values
+    "consistent-return": 1,
+
+    // Warn if no return statements in callbacks of array methods
+    "array-callback-return": 1,
+
+    // Requre the use of === and !==
+    "eqeqeq": 2,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    // Disallow the use of alert, confirm, and prompt
+    "no-alert": 2,
+
+    // Disallow the use of arguments.caller or arguments.callee
+    "no-caller": 2,
+
+    // Disallow null comparisons without type-checking operators
+    "no-eq-null": 2,
+
+    // Disallow the use of eval()
+    "no-eval": 2,
+
+    // Warn against extending native types
+    "no-extend-native": 1,
+
+    // Warn against unnecessary calls to .bind()
+    "no-extra-bind": 1,
+
+    // Warn against unnecessary labels    
+    "no-extra-label": 1,
+
+    // Disallow leading or trailing decimal points in numeric literals
+    "no-floating-decimal": 2,
+
+    // Warn against shorthand type conversions
+    "no-implicit-coercion": 1,
+
+    // Warn against function declarations and expressions inside loop statements
+    "no-loop-func": 1,
+
+    // Disallow new operators with the Function object
+    "no-new-func": 2,
+
+    // Warn against new operators with the String, Number, and Boolean objects
+    "no-new-wrappers": 1,
+
+    // Disallow throwing literals as exceptions
+    "no-throw-literal": 2,
+
+    // Require using Error objects as Promise rejection reasons
+    "prefer-promise-reject-errors": 2,
+
+    // Enforce “for” loop update clause moving the counter in the right direction
+    "for-direction": 2,
+
+    // Enforce return statements in getters
+    "getter-return": 2,
+
+    // Disallow await inside of loops
+    "no-await-in-loop": 2,
+
+    // Disallow comparing against -0
+    "no-compare-neg-zero": 2,
+
+    // Warn against catch clause parameters from shadowing variables in the outer scope
+    "no-catch-shadow": 1,
+
+    // Disallow identifiers from shadowing restricted names
+    "no-shadow-restricted-names": 2,
+
+    // Enforce return statements in callbacks of array methods
+    "callback-return": 2,
+
+    // Require error handling in callbacks
+    "handle-callback-err": 2,
+
+    // Warn against string concatenation with __dirname and __filename
+    "no-path-concat": 1,
+
+    // Prefer using arrow functions for callbacks
+    "prefer-arrow-callback": 1,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    //Enforces the use of catch() on un-returned promises
+    "promise/catch-or-return": 2,
+
+    // Warn against nested then() or catch() statements
+    "promise/no-nesting": 1
+  }
+}
diff --git a/nextjs-with-firebase-hosting/src/functions/index.js b/nextjs-with-firebase-hosting/src/functions/index.js
index 7be5506283..9e3cb779cd 100644
--- a/nextjs-with-firebase-hosting/src/functions/index.js
+++ b/nextjs-with-firebase-hosting/src/functions/index.js
@@ -2,7 +2,7 @@ const functions = require('firebase-functions');
 const next = require('next');
 
 var dev = process.env.NODE_ENV !== 'production';
-var app = next({ dev, conf: { distDir: 'next' } });
+var app = next({dev, conf: {distDir: 'next'}});
 var handle = app.getRequestHandler();
 
 exports.next = functions.https.onRequest((req, res) => {
diff --git a/paypal/functions/index.js b/paypal/functions/index.js
index 53f0734579..c039f6aa66 100644
--- a/paypal/functions/index.js
+++ b/paypal/functions/index.js
@@ -25,7 +25,7 @@ admin.initializeApp(functions.config().firebase);
 // Configure your environment
 paypal.configure({
   mode: 'sandbox', // sandbox or live
-  client_id: functions.config().paypal.client_id, // run: firebase functions:config:set paypal.client_id="yourPaypalClientID" 
+  client_id: functions.config().paypal.client_id, // run: firebase functions:config:set paypal.client_id="yourPaypalClientID"
   client_secret: functions.config().paypal.client_secret // run: firebase functions:config:set paypal.client_secret="yourPaypalClientSecret"
 });
 /**
@@ -34,56 +34,56 @@ paypal.configure({
  * Initialize the payment and redirect the user to the PayPal payment page
  */
 exports.pay = functions.https.onRequest((req, res) => {
-    // 1.Set up a payment information object, Nuild PayPal payment request
-    const payReq = JSON.stringify({
-        intent: 'sale',
-        payer: {
-          payment_method: 'paypal'
-        },
-        redirect_urls: {
-          return_url: `${req.protocol}://${req.get('host')}/process`,
-          cancel_url: `${req.protocol}://${req.get('host')}/cancel`
-        },
-        transactions: [{
-          amount: {
-            total: req.body.price,
-            currency: 'USD'
-          },
-          // This is the payment transaction description. Maximum length: 127
-          description: req.body.uid, // req.body.id
-          // reference_id string .Optional. The merchant-provided ID for the purchase unit. Maximum length: 256.
-          // reference_id: req.body.uid,
-          custom: req.body.uid,
-          // soft_descriptor: req.body.uid
-          // "invoice_number": req.body.uid,A
-        }]
-    });
-    // 2.Initialize the payment and redirect the user.
-    paypal.payment.create(payReq, (error, payment) => {
-        const links = {};
-        if (error) {
-            console.error(error);
-            res.status('500').end();
-        } else {
-            // Capture HATEOAS links
-            payment.links.forEach((linkObj) => {
-              links[linkObj.rel] = {
-                href: linkObj.href,
-                method: linkObj.method
-              };
-            });
-            // If redirect url present, redirect user
-            if (links.hasOwnProperty('approval_url')) {
-                // REDIRECT USER TO links['approval_url'].href
-                console.info(links.approval_url.href);
-                // res.json({"approval_url":links.approval_url.href});
-                res.redirect(302, links.approval_url.href);
-            } else {
-                console.error('no redirect URI present');
-                res.status('500').end();
-            }
-        }
-    });
+  // 1.Set up a payment information object, Nuild PayPal payment request
+  const payReq = JSON.stringify({
+    intent: 'sale',
+    payer: {
+      payment_method: 'paypal'
+    },
+    redirect_urls: {
+      return_url: `${req.protocol}://${req.get('host')}/process`,
+      cancel_url: `${req.protocol}://${req.get('host')}/cancel`
+    },
+    transactions: [{
+      amount: {
+        total: req.body.price,
+        currency: 'USD'
+      },
+      // This is the payment transaction description. Maximum length: 127
+      description: req.body.uid, // req.body.id
+      // reference_id string .Optional. The merchant-provided ID for the purchase unit. Maximum length: 256.
+      // reference_id: req.body.uid,
+      custom: req.body.uid,
+      // soft_descriptor: req.body.uid
+      // "invoice_number": req.body.uid,A
+    }]
+  });
+  // 2.Initialize the payment and redirect the user.
+  paypal.payment.create(payReq, (error, payment) => {
+    const links = {};
+    if (error) {
+      console.error(error);
+      res.status('500').end();
+    } else {
+      // Capture HATEOAS links
+      payment.links.forEach((linkObj) => {
+        links[linkObj.rel] = {
+          href: linkObj.href,
+          method: linkObj.method
+        };
+      });
+      // If redirect url present, redirect user
+      if (links.hasOwnProperty('approval_url')) {
+        // REDIRECT USER TO links['approval_url'].href
+        console.info(links.approval_url.href);
+        // res.json({"approval_url":links.approval_url.href});
+        res.redirect(302, links.approval_url.href);
+      } else {
+        console.error('no redirect URI present');
+        res.status('500').end();
+      }
+    }
+  });
 });
 
 // 3.Complete the payment. Use the payer and payment IDs provided in the query string following the redirect.
@@ -92,7 +92,7 @@ exports.process = functions.https.onRequest((req, res) => {
   const payerId = {
     payer_id: req.query.PayerID
   };
-  paypal.payment.execute(paymentId, payerId, (error, payment) => {
+  return paypal.payment.execute(paymentId, payerId, (error, payment) => {
     if (error) {
       console.error(error);
       res.redirect(`${req.protocol}://${req.get('host')}/error`); // replace with your url page error
@@ -108,7 +108,7 @@ exports.process = functions.https.onRequest((req, res) => {
           'paid': true,
           // 'description': description,
           'date': date
-        }).then(r => console.info('promise: ', r));
+        })
         res.redirect(`${req.protocol}://${req.get('host')}/success`); // replace with your url, page success
       } else {
         console.warn('payment.state: not approved ?');
@@ -116,5 +116,5 @@ exports.process = functions.https.onRequest((req, res) => {
         res.redirect(`https://console.firebase.google.com/project/${process.env.GCLOUD_PROJECT}/functions/logs?search=&severity=DEBUG`);
       }
     }
-  });
+  }).then(r => console.info('promise: ', r));
 });
diff --git a/presence-firestore/functions/.eslintrc.json b/presence-firestore/functions/.eslintrc.json
new file mode 100644
index 0000000000..eb4c93169b
--- /dev/null
+++ b/presence-firestore/functions/.eslintrc.json
@@ -0,0 +1,125 @@
+{
+  "parserOptions": {
+    // Required for certain syntax usages
+    "ecmaVersion": 6
+  },
+  "plugins": [
+    "promise"
+  ],
+  "extends": "eslint:recommended",
+  "rules": {
+    // Removed rule "disallow the use of console" from recommended eslint rules
+    "no-console": "off",
+
+    // Removed rule "disallow multiple spaces in regular expressions" from recommended eslint rules
+    "no-regex-spaces": "off",
+
+    // Removed rule "disallow the use of debugger" from recommended eslint rules
+    "no-debugger": "off",
+
+    // Removed rule "disallow unused variables" from recommended eslint rules
+    "no-unused-vars": "off",
+
+    // Removed rule "disallow mixed spaces and tabs for indentation" from recommended eslint rules
+    "no-mixed-spaces-and-tabs": "off",
+
+    // Removed rule "disallow the use of undeclared variables unless mentioned in /*global */ comments" from recommended eslint rules
+    "no-undef": "off",
+
+    // Warn against template literal placeholder syntax in regular strings
+    "no-template-curly-in-string": 1,
+
+    // Warn if return statements do not either always or never specify values
+    "consistent-return": 1,
+
+    // Warn if no return statements in callbacks of array methods
+    "array-callback-return": 1,
+
+    // Requre the use of === and !==
+    "eqeqeq": 2,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    // Disallow the use of alert, confirm, and prompt
+    "no-alert": 2,
+
+    // Disallow the use of arguments.caller or arguments.callee
+    "no-caller": 2,
+
+    // Disallow null comparisons without type-checking operators
+    "no-eq-null": 2,
+
+    // Disallow the use of eval()
+    "no-eval": 2,
+
+    // Warn against extending native types
+    "no-extend-native": 1,
+
+    // Warn against unnecessary calls to .bind()
+    "no-extra-bind": 1,
+
+    // Warn against unnecessary labels    
+    "no-extra-label": 1,
+
+    // Disallow leading or trailing decimal points in numeric literals
+    "no-floating-decimal": 2,
+
+    // Warn against shorthand type conversions
+    "no-implicit-coercion": 1,
+
+    // Warn against function declarations and expressions inside loop statements
+    "no-loop-func": 1,
+
+    // Disallow new operators with the Function object
+    "no-new-func": 2,
+
+    // Warn against new operators with the String, Number, and Boolean objects
+    "no-new-wrappers": 1,
+
+    // Disallow throwing literals as exceptions
+    "no-throw-literal": 2,
+
+    // Require using Error objects as Promise rejection reasons
+    "prefer-promise-reject-errors": 2,
+
+    // Enforce “for” loop update clause moving the counter in the right direction
+    "for-direction": 2,
+
+    // Enforce return statements in getters
+    "getter-return": 2,
+
+    // Disallow await inside of loops
+    "no-await-in-loop": 2,
+
+    // Disallow comparing against -0
+    "no-compare-neg-zero": 2,
+
+    // Warn against catch clause parameters from shadowing variables in the outer scope
+    "no-catch-shadow": 1,
+
+    // Disallow identifiers from shadowing restricted names
+    "no-shadow-restricted-names": 2,
+
+    // Enforce return statements in callbacks of array methods
+    "callback-return": 2,
+
+    // Require error handling in callbacks
+    "handle-callback-err": 2,
+
+    // Warn against string concatenation with __dirname and __filename
+    "no-path-concat": 1,
+
+    // Prefer using arrow functions for callbacks
+    "prefer-arrow-callback": 1,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    //Enforces the use of catch() on un-returned promises
+    "promise/catch-or-return": 2,
+
+    // Warn against nested then() or catch() statements
+    "promise/no-nesting": 1
+  }
+}
diff --git a/presence-firestore/functions/index.js b/presence-firestore/functions/index.js
index e4be40116e..c1981b00c5 100644
--- a/presence-firestore/functions/index.js
+++ b/presence-firestore/functions/index.js
@@ -27,31 +27,30 @@ const firestore = admin.firestore();
 
 // Create a new function which is triggered on changes to /status/{uid}
 // Note: This is a Realtime Database trigger, *not* Cloud Firestore.
-exports.onUserStatusChanged = functions.database
-    .ref('/status/{uid}').onUpdate(event => {
-        // Get the data written to Realtime Database
-        const eventStatus = event.data.val();
-
-        // Then use other event data to create a reference to the
-        // corresponding Firestore document.
-        const userStatusFirestoreRef = firestore.doc(`status/${event.params.uid}`);
-
-        // It is likely that the Realtime Database change that triggered
-        // this event has already been overwritten by a fast change in
-        // online / offline status, so we'll re-read the current data
-        // and compare the timestamps.
-        return event.data.ref.once('value').then(statusSnapshot => {
-            const status = statusSnapshot.val();
-            console.log(status, eventStatus);
-            // If the current timestamp for this data is newer than
-            // the data that triggered this event, we exit this function.
-            if (status.last_changed > eventStatus.last_changed) return;
-
-            // Otherwise, we convert the last_changed field to a Date
-            eventStatus.last_changed = new Date(eventStatus.last_changed);
-
-            // ... and write it to Firestore.
-            return userStatusFirestoreRef.set(eventStatus);
-        });
-    });
+exports.onUserStatusChanged = functions.database.ref('/status/{uid}').onUpdate((event) => {
+  // Get the data written to Realtime Database
+  const eventStatus = event.data.val();
+
+  // Then use other event data to create a reference to the
+  // corresponding Firestore document.
+  const userStatusFirestoreRef = firestore.doc(`status/${event.params.uid}`);
+
+  // It is likely that the Realtime Database change that triggered
+  // this event has already been overwritten by a fast change in
+  // online / offline status, so we'll re-read the current data
+  // and compare the timestamps.
+  return event.data.ref.once('value').then((statusSnapshot) => {
+    const status = statusSnapshot.val();
+    console.log(status, eventStatus);
+    // If the current timestamp for this data is newer than
+    // the data that triggered this event, we exit this function.
+    if (status.last_changed > eventStatus.last_changed) return null;
+
+    // Otherwise, we convert the last_changed field to a Date
+    eventStatus.last_changed = new Date(eventStatus.last_changed);
+
+    // ... and write it to Firestore.
+    return userStatusFirestoreRef.set(eventStatus);
+  });
+});
 // [END presence_sync_function]
diff --git a/quickstarts/big-ben/functions/.eslintrc.json b/quickstarts/big-ben/functions/.eslintrc.json
new file mode 100644
index 0000000000..eb4c93169b
--- /dev/null
+++ b/quickstarts/big-ben/functions/.eslintrc.json
@@ -0,0 +1,125 @@
+{
+  "parserOptions": {
+    // Required for certain syntax usages
+    "ecmaVersion": 6
+  },
+  "plugins": [
+    "promise"
+  ],
+  "extends": "eslint:recommended",
+  "rules": {
+    // Removed rule "disallow the use of console" from recommended eslint rules
+    "no-console": "off",
+
+    // Removed rule "disallow multiple spaces in regular expressions" from recommended eslint rules
+    "no-regex-spaces": "off",
+
+    // Removed rule "disallow the use of debugger" from recommended eslint rules
+    "no-debugger": "off",
+
+    // Removed rule "disallow unused variables" from recommended eslint rules
+    "no-unused-vars": "off",
+
+    // Removed rule "disallow mixed spaces and tabs for indentation" from recommended eslint rules
+    "no-mixed-spaces-and-tabs": "off",
+
+    // Removed rule "disallow the use of undeclared variables unless mentioned in /*global */ comments" from recommended eslint rules
+    "no-undef": "off",
+
+    // Warn against template literal placeholder syntax in regular strings
+    "no-template-curly-in-string": 1,
+
+    // Warn if return statements do not either always or never specify values
+    "consistent-return": 1,
+
+    // Warn if no return statements in callbacks of array methods
+    "array-callback-return": 1,
+
+    // Requre the use of === and !==
+    "eqeqeq": 2,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    // Disallow the use of alert, confirm, and prompt
+    "no-alert": 2,
+
+    // Disallow the use of arguments.caller or arguments.callee
+    "no-caller": 2,
+
+    // Disallow null comparisons without type-checking operators
+    "no-eq-null": 2,
+
+    // Disallow the use of eval()
+    "no-eval": 2,
+
+    // Warn against extending native types
+    "no-extend-native": 1,
+
+    // Warn against unnecessary calls to .bind()
+    "no-extra-bind": 1,
+
+    // Warn against unnecessary labels    
+    "no-extra-label": 1,
+
+    // Disallow leading or trailing decimal points in numeric literals
+    "no-floating-decimal": 2,
+
+    // Warn against shorthand type conversions
+    "no-implicit-coercion": 1,
+
+    // Warn against function declarations and expressions inside loop statements
+    "no-loop-func": 1,
+
+    // Disallow new operators with the Function object
+    "no-new-func": 2,
+
+    // Warn against new operators with the String, Number, and Boolean objects
+    "no-new-wrappers": 1,
+
+    // Disallow throwing literals as exceptions
+    "no-throw-literal": 2,
+
+    // Require using Error objects as Promise rejection reasons
+    "prefer-promise-reject-errors": 2,
+
+    // Enforce “for” loop update clause moving the counter in the right direction
+    "for-direction": 2,
+
+    // Enforce return statements in getters
+    "getter-return": 2,
+
+    // Disallow await inside of loops
+    "no-await-in-loop": 2,
+
+    // Disallow comparing against -0
+    "no-compare-neg-zero": 2,
+
+    // Warn against catch clause parameters from shadowing variables in the outer scope
+    "no-catch-shadow": 1,
+
+    // Disallow identifiers from shadowing restricted names
+    "no-shadow-restricted-names": 2,
+
+    // Enforce return statements in callbacks of array methods
+    "callback-return": 2,
+
+    // Require error handling in callbacks
+    "handle-callback-err": 2,
+
+    // Warn against string concatenation with __dirname and __filename
+    "no-path-concat": 1,
+
+    // Prefer using arrow functions for callbacks
+    "prefer-arrow-callback": 1,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    //Enforces the use of catch() on un-returned promises
+    "promise/catch-or-return": 2,
+
+    // Warn against nested then() or catch() statements
+    "promise/no-nesting": 1
+  }
+}
diff --git a/quickstarts/email-users/functions/.eslintrc.json b/quickstarts/email-users/functions/.eslintrc.json
new file mode 100644
index 0000000000..eb4c93169b
--- /dev/null
+++ b/quickstarts/email-users/functions/.eslintrc.json
@@ -0,0 +1,125 @@
+{
+  "parserOptions": {
+    // Required for certain syntax usages
+    "ecmaVersion": 6
+  },
+  "plugins": [
+    "promise"
+  ],
+  "extends": "eslint:recommended",
+  "rules": {
+    // Removed rule "disallow the use of console" from recommended eslint rules
+    "no-console": "off",
+
+    // Removed rule "disallow multiple spaces in regular expressions" from recommended eslint rules
+    "no-regex-spaces": "off",
+
+    // Removed rule "disallow the use of debugger" from recommended eslint rules
+    "no-debugger": "off",
+
+    // Removed rule "disallow unused variables" from recommended eslint rules
+    "no-unused-vars": "off",
+
+    // Removed rule "disallow mixed spaces and tabs for indentation" from recommended eslint rules
+    "no-mixed-spaces-and-tabs": "off",
+
+    // Removed rule "disallow the use of undeclared variables unless mentioned in /*global */ comments" from recommended eslint rules
+    "no-undef": "off",
+
+    // Warn against template literal placeholder syntax in regular strings
+    "no-template-curly-in-string": 1,
+
+    // Warn if return statements do not either always or never specify values
+    "consistent-return": 1,
+
+    // Warn if no return statements in callbacks of array methods
+    "array-callback-return": 1,
+
+    // Requre the use of === and !==
+    "eqeqeq": 2,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    // Disallow the use of alert, confirm, and prompt
+    "no-alert": 2,
+
+    // Disallow the use of arguments.caller or arguments.callee
+    "no-caller": 2,
+
+    // Disallow null comparisons without type-checking operators
+    "no-eq-null": 2,
+
+    // Disallow the use of eval()
+    "no-eval": 2,
+
+    // Warn against extending native types
+    "no-extend-native": 1,
+
+    // Warn against unnecessary calls to .bind()
+    "no-extra-bind": 1,
+
+    // Warn against unnecessary labels    
+    "no-extra-label": 1,
+
+    // Disallow leading or trailing decimal points in numeric literals
+    "no-floating-decimal": 2,
+
+    // Warn against shorthand type conversions
+    "no-implicit-coercion": 1,
+
+    // Warn against function declarations and expressions inside loop statements
+    "no-loop-func": 1,
+
+    // Disallow new operators with the Function object
+    "no-new-func": 2,
+
+    // Warn against new operators with the String, Number, and Boolean objects
+    "no-new-wrappers": 1,
+
+    // Disallow throwing literals as exceptions
+    "no-throw-literal": 2,
+
+    // Require using Error objects as Promise rejection reasons
+    "prefer-promise-reject-errors": 2,
+
+    // Enforce “for” loop update clause moving the counter in the right direction
+    "for-direction": 2,
+
+    // Enforce return statements in getters
+    "getter-return": 2,
+
+    // Disallow await inside of loops
+    "no-await-in-loop": 2,
+
+    // Disallow comparing against -0
+    "no-compare-neg-zero": 2,
+
+    // Warn against catch clause parameters from shadowing variables in the outer scope
+    "no-catch-shadow": 1,
+
+    // Disallow identifiers from shadowing restricted names
+    "no-shadow-restricted-names": 2,
+
+    // Enforce return statements in callbacks of array methods
+    "callback-return": 2,
+
+    // Require error handling in callbacks
+    "handle-callback-err": 2,
+
+    // Warn against string concatenation with __dirname and __filename
+    "no-path-concat": 1,
+
+    // Prefer using arrow functions for callbacks
+    "prefer-arrow-callback": 1,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    //Enforces the use of catch() on un-returned promises
+    "promise/catch-or-return": 2,
+
+    // Warn against nested then() or catch() statements
+    "promise/no-nesting": 1
+  }
+}
diff --git a/quickstarts/email-users/functions/index.js b/quickstarts/email-users/functions/index.js
index caa14c289d..d7995e36b7 100644
--- a/quickstarts/email-users/functions/index.js
+++ b/quickstarts/email-users/functions/index.js
@@ -29,8 +29,8 @@ const mailTransport = nodemailer.createTransport({
   service: 'gmail',
   auth: {
     user: gmailEmail,
-    pass: gmailPassword
-  }
+    pass: gmailPassword,
+  },
 });
 
 // Your company name to include in the emails
@@ -42,8 +42,8 @@ const APP_NAME = 'Cloud Storage for Firebase quickstart';
  * Sends a welcome email to new user.
  */
 // [START onCreateTrigger]
-exports.sendWelcomeEmail = functions.auth.user().onCreate(event => {
-// [END onCreateTrigger]
+exports.sendWelcomeEmail = functions.auth.user().onCreate((event) => {
+  // [END onCreateTrigger]
   // [START eventAttributes]
   const user = event.data; // The Firebase user.
 
@@ -60,8 +60,8 @@ exports.sendWelcomeEmail = functions.auth.user().onCreate(event => {
  * Send an account deleted email confirmation to users who delete their accounts.
  */
 // [START onDeleteTrigger]
-exports.sendByeEmail = functions.auth.user().onDelete(event => {
-// [END onDeleteTrigger]
+exports.sendByeEmail = functions.auth.user().onDelete((event) => {
+  // [END onDeleteTrigger]
   const user = event.data;
 
   const email = user.email;
@@ -75,14 +75,14 @@ exports.sendByeEmail = functions.auth.user().onDelete(event => {
 function sendWelcomeEmail(email, displayName) {
   const mailOptions = {
     from: `${APP_NAME} <noreply@firebase.com>`,
-    to: email
+    to: email,
   };
 
   // The user subscribed to the newsletter.
   mailOptions.subject = `Welcome to ${APP_NAME}!`;
   mailOptions.text = `Hey ${displayName || ''}! Welcome to ${APP_NAME}. I hope you will enjoy our service.`;
   return mailTransport.sendMail(mailOptions).then(() => {
-    console.log('New welcome email sent to:', email);
+    return console.log('New welcome email sent to:', email);
   });
 }
 
@@ -90,13 +90,13 @@ function sendWelcomeEmail(email, displayName) {
 function sendGoodbyEmail(email, displayName) {
   const mailOptions = {
     from: `${APP_NAME} <noreply@firebase.com>`,
-    to: email
+    to: email,
   };
 
   // The user unsubscribed to the newsletter.
   mailOptions.subject = `Bye!`;
   mailOptions.text = `Hey ${displayName || ''}!, We confirm that we have deleted your ${APP_NAME} account.`;
   return mailTransport.sendMail(mailOptions).then(() => {
-    console.log('Account deletion confirmation email sent to:', email);
+    return console.log('Account deletion confirmation email sent to:', email);
   });
 }
diff --git a/quickstarts/pubsub-helloworld/functions/.eslintrc.json b/quickstarts/pubsub-helloworld/functions/.eslintrc.json
new file mode 100644
index 0000000000..eb4c93169b
--- /dev/null
+++ b/quickstarts/pubsub-helloworld/functions/.eslintrc.json
@@ -0,0 +1,125 @@
+{
+  "parserOptions": {
+    // Required for certain syntax usages
+    "ecmaVersion": 6
+  },
+  "plugins": [
+    "promise"
+  ],
+  "extends": "eslint:recommended",
+  "rules": {
+    // Removed rule "disallow the use of console" from recommended eslint rules
+    "no-console": "off",
+
+    // Removed rule "disallow multiple spaces in regular expressions" from recommended eslint rules
+    "no-regex-spaces": "off",
+
+    // Removed rule "disallow the use of debugger" from recommended eslint rules
+    "no-debugger": "off",
+
+    // Removed rule "disallow unused variables" from recommended eslint rules
+    "no-unused-vars": "off",
+
+    // Removed rule "disallow mixed spaces and tabs for indentation" from recommended eslint rules
+    "no-mixed-spaces-and-tabs": "off",
+
+    // Removed rule "disallow the use of undeclared variables unless mentioned in /*global */ comments" from recommended eslint rules
+    "no-undef": "off",
+
+    // Warn against template literal placeholder syntax in regular strings
+    "no-template-curly-in-string": 1,
+
+    // Warn if return statements do not either always or never specify values
+    "consistent-return": 1,
+
+    // Warn if no return statements in callbacks of array methods
+    "array-callback-return": 1,
+
+    // Requre the use of === and !==
+    "eqeqeq": 2,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    // Disallow the use of alert, confirm, and prompt
+    "no-alert": 2,
+
+    // Disallow the use of arguments.caller or arguments.callee
+    "no-caller": 2,
+
+    // Disallow null comparisons without type-checking operators
+    "no-eq-null": 2,
+
+    // Disallow the use of eval()
+    "no-eval": 2,
+
+    // Warn against extending native types
+    "no-extend-native": 1,
+
+    // Warn against unnecessary calls to .bind()
+    "no-extra-bind": 1,
+
+    // Warn against unnecessary labels    
+    "no-extra-label": 1,
+
+    // Disallow leading or trailing decimal points in numeric literals
+    "no-floating-decimal": 2,
+
+    // Warn against shorthand type conversions
+    "no-implicit-coercion": 1,
+
+    // Warn against function declarations and expressions inside loop statements
+    "no-loop-func": 1,
+
+    // Disallow new operators with the Function object
+    "no-new-func": 2,
+
+    // Warn against new operators with the String, Number, and Boolean objects
+    "no-new-wrappers": 1,
+
+    // Disallow throwing literals as exceptions
+    "no-throw-literal": 2,
+
+    // Require using Error objects as Promise rejection reasons
+    "prefer-promise-reject-errors": 2,
+
+    // Enforce “for” loop update clause moving the counter in the right direction
+    "for-direction": 2,
+
+    // Enforce return statements in getters
+    "getter-return": 2,
+
+    // Disallow await inside of loops
+    "no-await-in-loop": 2,
+
+    // Disallow comparing against -0
+    "no-compare-neg-zero": 2,
+
+    // Warn against catch clause parameters from shadowing variables in the outer scope
+    "no-catch-shadow": 1,
+
+    // Disallow identifiers from shadowing restricted names
+    "no-shadow-restricted-names": 2,
+
+    // Enforce return statements in callbacks of array methods
+    "callback-return": 2,
+
+    // Require error handling in callbacks
+    "handle-callback-err": 2,
+
+    // Warn against string concatenation with __dirname and __filename
+    "no-path-concat": 1,
+
+    // Prefer using arrow functions for callbacks
+    "prefer-arrow-callback": 1,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    //Enforces the use of catch() on un-returned promises
+    "promise/catch-or-return": 2,
+
+    // Warn against nested then() or catch() statements
+    "promise/no-nesting": 1
+  }
+}
diff --git a/quickstarts/pubsub-helloworld/functions/index.js b/quickstarts/pubsub-helloworld/functions/index.js
index fe33cdb5d7..a937a6a5f2 100644
--- a/quickstarts/pubsub-helloworld/functions/index.js
+++ b/quickstarts/pubsub-helloworld/functions/index.js
@@ -25,7 +25,7 @@ const functions = require('firebase-functions');
  * topic.
  */
 // [START trigger]
-exports.helloPubSub = functions.pubsub.topic('topic-name').onPublish(event => {
+exports.helloPubSub = functions.pubsub.topic('topic-name').onPublish((event) => {
 // [END trigger]
   // [START readBase64]
   const pubSubMessage = event.data;
@@ -41,7 +41,7 @@ exports.helloPubSub = functions.pubsub.topic('topic-name').onPublish(event => {
  * Cloud Function to be triggered by Pub/Sub that logs a message using the data published to the
  * topic as JSON.
  */
-exports.helloPubSubJson = functions.pubsub.topic('another-topic-name').onPublish(event => {
+exports.helloPubSubJson = functions.pubsub.topic('another-topic-name').onPublish((event) => {
   // [START readJson]
   const pubSubMessage = event.data;
   // Get the `name` attribute of the PubSub message JSON body.
@@ -60,7 +60,7 @@ exports.helloPubSubJson = functions.pubsub.topic('another-topic-name').onPublish
  * Cloud Function to be triggered by Pub/Sub that logs a message using the data attributes
  * published to the topic.
  */
-exports.helloPubSubAttributes = functions.pubsub.topic('yet-another-topic-name').onPublish(event => {
+exports.helloPubSubAttributes = functions.pubsub.topic('yet-another-topic-name').onPublish((event) => {
   // [START readAttributes]
   const pubSubMessage = event.data;
   // Get the `name` attribute of the message.
diff --git a/quickstarts/thumbnails/functions/.eslintrc.json b/quickstarts/thumbnails/functions/.eslintrc.json
new file mode 100644
index 0000000000..eb4c93169b
--- /dev/null
+++ b/quickstarts/thumbnails/functions/.eslintrc.json
@@ -0,0 +1,125 @@
+{
+  "parserOptions": {
+    // Required for certain syntax usages
+    "ecmaVersion": 6
+  },
+  "plugins": [
+    "promise"
+  ],
+  "extends": "eslint:recommended",
+  "rules": {
+    // Removed rule "disallow the use of console" from recommended eslint rules
+    "no-console": "off",
+
+    // Removed rule "disallow multiple spaces in regular expressions" from recommended eslint rules
+    "no-regex-spaces": "off",
+
+    // Removed rule "disallow the use of debugger" from recommended eslint rules
+    "no-debugger": "off",
+
+    // Removed rule "disallow unused variables" from recommended eslint rules
+    "no-unused-vars": "off",
+
+    // Removed rule "disallow mixed spaces and tabs for indentation" from recommended eslint rules
+    "no-mixed-spaces-and-tabs": "off",
+
+    // Removed rule "disallow the use of undeclared variables unless mentioned in /*global */ comments" from recommended eslint rules
+    "no-undef": "off",
+
+    // Warn against template literal placeholder syntax in regular strings
+    "no-template-curly-in-string": 1,
+
+    // Warn if return statements do not either always or never specify values
+    "consistent-return": 1,
+
+    // Warn if no return statements in callbacks of array methods
+    "array-callback-return": 1,
+
+    // Requre the use of === and !==
+    "eqeqeq": 2,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    // Disallow the use of alert, confirm, and prompt
+    "no-alert": 2,
+
+    // Disallow the use of arguments.caller or arguments.callee
+    "no-caller": 2,
+
+    // Disallow null comparisons without type-checking operators
+    "no-eq-null": 2,
+
+    // Disallow the use of eval()
+    "no-eval": 2,
+
+    // Warn against extending native types
+    "no-extend-native": 1,
+
+    // Warn against unnecessary calls to .bind()
+    "no-extra-bind": 1,
+
+    // Warn against unnecessary labels    
+    "no-extra-label": 1,
+
+    // Disallow leading or trailing decimal points in numeric literals
+    "no-floating-decimal": 2,
+
+    // Warn against shorthand type conversions
+    "no-implicit-coercion": 1,
+
+    // Warn against function declarations and expressions inside loop statements
+    "no-loop-func": 1,
+
+    // Disallow new operators with the Function object
+    "no-new-func": 2,
+
+    // Warn against new operators with the String, Number, and Boolean objects
+    "no-new-wrappers": 1,
+
+    // Disallow throwing literals as exceptions
+    "no-throw-literal": 2,
+
+    // Require using Error objects as Promise rejection reasons
+    "prefer-promise-reject-errors": 2,
+
+    // Enforce “for” loop update clause moving the counter in the right direction
+    "for-direction": 2,
+
+    // Enforce return statements in getters
+    "getter-return": 2,
+
+    // Disallow await inside of loops
+    "no-await-in-loop": 2,
+
+    // Disallow comparing against -0
+    "no-compare-neg-zero": 2,
+
+    // Warn against catch clause parameters from shadowing variables in the outer scope
+    "no-catch-shadow": 1,
+
+    // Disallow identifiers from shadowing restricted names
+    "no-shadow-restricted-names": 2,
+
+    // Enforce return statements in callbacks of array methods
+    "callback-return": 2,
+
+    // Require error handling in callbacks
+    "handle-callback-err": 2,
+
+    // Warn against string concatenation with __dirname and __filename
+    "no-path-concat": 1,
+
+    // Prefer using arrow functions for callbacks
+    "prefer-arrow-callback": 1,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    //Enforces the use of catch() on un-returned promises
+    "promise/catch-or-return": 2,
+
+    // Warn against nested then() or catch() statements
+    "promise/no-nesting": 1
+  }
+}
diff --git a/quickstarts/thumbnails/functions/index.js b/quickstarts/thumbnails/functions/index.js
index 7d269fc64f..df15bde524 100644
--- a/quickstarts/thumbnails/functions/index.js
+++ b/quickstarts/thumbnails/functions/index.js
@@ -30,8 +30,8 @@ const fs = require('fs');
  * ImageMagick.
  */
 // [START generateThumbnailTrigger]
-exports.generateThumbnail = functions.storage.object().onChange(event => {
-// [END generateThumbnailTrigger]
+exports.generateThumbnail = functions.storage.object().onChange((event) => {
+  // [END generateThumbnailTrigger]
   // [START eventAttributes]
   const object = event.data; // The Storage object.
 
@@ -46,7 +46,7 @@ exports.generateThumbnail = functions.storage.object().onChange(event => {
   // Exit if this is triggered on a file that is not an image.
   if (!contentType.startsWith('image/')) {
     console.log('This is not an image.');
-    return;
+    return null;
   }
 
   // Get the file name.
@@ -54,20 +54,20 @@ exports.generateThumbnail = functions.storage.object().onChange(event => {
   // Exit if the image is already a thumbnail.
   if (fileName.startsWith('thumb_')) {
     console.log('Already a Thumbnail.');
-    return;
+    return null;
   }
 
   // Exit if this is a move or deletion event.
   if (resourceState === 'not_exists') {
     console.log('This is a deletion event.');
-    return;
+    return null;
   }
 
   // Exit if file exists but is not new and is only being triggered
   // because of a metadata change.
   if (resourceState === 'exists' && metageneration > 1) {
     console.log('This is a metadata change event.');
-    return;
+    return null;
   }
   // [END stopConditions]
 
@@ -75,9 +75,11 @@ exports.generateThumbnail = functions.storage.object().onChange(event => {
   // Download file from bucket.
   const bucket = gcs.bucket(fileBucket);
   const tempFilePath = path.join(os.tmpdir(), fileName);
-  const metadata = { contentType: contentType };
+  const metadata = {
+    contentType: contentType,
+  };
   return bucket.file(filePath).download({
-    destination: tempFilePath
+    destination: tempFilePath,
   }).then(() => {
     console.log('Image downloaded locally to', tempFilePath);
     // Generate a thumbnail using ImageMagick.
@@ -88,8 +90,11 @@ exports.generateThumbnail = functions.storage.object().onChange(event => {
     const thumbFileName = `thumb_${fileName}`;
     const thumbFilePath = path.join(path.dirname(filePath), thumbFileName);
     // Uploading the thumbnail.
-    return bucket.upload(tempFilePath, { destination: thumbFilePath, metadata: metadata });
-  // Once the thumbnail has been uploaded delete the local file to free up disk space.
+    return bucket.upload(tempFilePath, {
+      destination: thumbFilePath,
+      metadata: metadata,
+    });
+    // Once the thumbnail has been uploaded delete the local file to free up disk space.
   }).then(() => fs.unlinkSync(tempFilePath));
   // [END thumbnailGeneration]
 });
diff --git a/quickstarts/time-server/functions/.eslintrc.json b/quickstarts/time-server/functions/.eslintrc.json
new file mode 100644
index 0000000000..eb4c93169b
--- /dev/null
+++ b/quickstarts/time-server/functions/.eslintrc.json
@@ -0,0 +1,125 @@
+{
+  "parserOptions": {
+    // Required for certain syntax usages
+    "ecmaVersion": 6
+  },
+  "plugins": [
+    "promise"
+  ],
+  "extends": "eslint:recommended",
+  "rules": {
+    // Removed rule "disallow the use of console" from recommended eslint rules
+    "no-console": "off",
+
+    // Removed rule "disallow multiple spaces in regular expressions" from recommended eslint rules
+    "no-regex-spaces": "off",
+
+    // Removed rule "disallow the use of debugger" from recommended eslint rules
+    "no-debugger": "off",
+
+    // Removed rule "disallow unused variables" from recommended eslint rules
+    "no-unused-vars": "off",
+
+    // Removed rule "disallow mixed spaces and tabs for indentation" from recommended eslint rules
+    "no-mixed-spaces-and-tabs": "off",
+
+    // Removed rule "disallow the use of undeclared variables unless mentioned in /*global */ comments" from recommended eslint rules
+    "no-undef": "off",
+
+    // Warn against template literal placeholder syntax in regular strings
+    "no-template-curly-in-string": 1,
+
+    // Warn if return statements do not either always or never specify values
+    "consistent-return": 1,
+
+    // Warn if no return statements in callbacks of array methods
+    "array-callback-return": 1,
+
+    // Requre the use of === and !==
+    "eqeqeq": 2,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    // Disallow the use of alert, confirm, and prompt
+    "no-alert": 2,
+
+    // Disallow the use of arguments.caller or arguments.callee
+    "no-caller": 2,
+
+    // Disallow null comparisons without type-checking operators
+    "no-eq-null": 2,
+
+    // Disallow the use of eval()
+    "no-eval": 2,
+
+    // Warn against extending native types
+    "no-extend-native": 1,
+
+    // Warn against unnecessary calls to .bind()
+    "no-extra-bind": 1,
+
+    // Warn against unnecessary labels    
+    "no-extra-label": 1,
+
+    // Disallow leading or trailing decimal points in numeric literals
+    "no-floating-decimal": 2,
+
+    // Warn against shorthand type conversions
+    "no-implicit-coercion": 1,
+
+    // Warn against function declarations and expressions inside loop statements
+    "no-loop-func": 1,
+
+    // Disallow new operators with the Function object
+    "no-new-func": 2,
+
+    // Warn against new operators with the String, Number, and Boolean objects
+    "no-new-wrappers": 1,
+
+    // Disallow throwing literals as exceptions
+    "no-throw-literal": 2,
+
+    // Require using Error objects as Promise rejection reasons
+    "prefer-promise-reject-errors": 2,
+
+    // Enforce “for” loop update clause moving the counter in the right direction
+    "for-direction": 2,
+
+    // Enforce return statements in getters
+    "getter-return": 2,
+
+    // Disallow await inside of loops
+    "no-await-in-loop": 2,
+
+    // Disallow comparing against -0
+    "no-compare-neg-zero": 2,
+
+    // Warn against catch clause parameters from shadowing variables in the outer scope
+    "no-catch-shadow": 1,
+
+    // Disallow identifiers from shadowing restricted names
+    "no-shadow-restricted-names": 2,
+
+    // Enforce return statements in callbacks of array methods
+    "callback-return": 2,
+
+    // Require error handling in callbacks
+    "handle-callback-err": 2,
+
+    // Warn against string concatenation with __dirname and __filename
+    "no-path-concat": 1,
+
+    // Prefer using arrow functions for callbacks
+    "prefer-arrow-callback": 1,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    //Enforces the use of catch() on un-returned promises
+    "promise/catch-or-return": 2,
+
+    // Warn against nested then() or catch() statements
+    "promise/no-nesting": 1
+  }
+}
diff --git a/quickstarts/time-server/functions/index.js b/quickstarts/time-server/functions/index.js
index 88a0c9aeb3..839e833ff7 100644
--- a/quickstarts/time-server/functions/index.js
+++ b/quickstarts/time-server/functions/index.js
@@ -22,7 +22,9 @@ const functions = require('firebase-functions');
 // Moments library to format dates.
 const moment = require('moment');
 // CORS Express middleware to enable CORS Requests.
-const cors = require('cors')({origin: true});
+const cors = require('cors')({
+  origin: true,
+});
 // [END additionalimports]
 
 // [START all]
@@ -44,7 +46,7 @@ const cors = require('cors')({origin: true});
  */
 // [START trigger]
 exports.date = functions.https.onRequest((req, res) => {
-// [END trigger]
+  // [END trigger]
   // [START sendError]
   // Forbidding PUT requests.
   if (req.method === 'PUT') {
@@ -55,7 +57,7 @@ exports.date = functions.https.onRequest((req, res) => {
   // [START usingMiddleware]
   // Enable CORS using the `cors` express middleware.
   cors(req, res, () => {
-  // [END usingMiddleware]
+    // [END usingMiddleware]
     // Reading date format from URL query parameter.
     // [START readQueryParam]
     let format = req.query.format;
diff --git a/quickstarts/uppercase-firestore/functions/.eslintrc.json b/quickstarts/uppercase-firestore/functions/.eslintrc.json
new file mode 100644
index 0000000000..eb4c93169b
--- /dev/null
+++ b/quickstarts/uppercase-firestore/functions/.eslintrc.json
@@ -0,0 +1,125 @@
+{
+  "parserOptions": {
+    // Required for certain syntax usages
+    "ecmaVersion": 6
+  },
+  "plugins": [
+    "promise"
+  ],
+  "extends": "eslint:recommended",
+  "rules": {
+    // Removed rule "disallow the use of console" from recommended eslint rules
+    "no-console": "off",
+
+    // Removed rule "disallow multiple spaces in regular expressions" from recommended eslint rules
+    "no-regex-spaces": "off",
+
+    // Removed rule "disallow the use of debugger" from recommended eslint rules
+    "no-debugger": "off",
+
+    // Removed rule "disallow unused variables" from recommended eslint rules
+    "no-unused-vars": "off",
+
+    // Removed rule "disallow mixed spaces and tabs for indentation" from recommended eslint rules
+    "no-mixed-spaces-and-tabs": "off",
+
+    // Removed rule "disallow the use of undeclared variables unless mentioned in /*global */ comments" from recommended eslint rules
+    "no-undef": "off",
+
+    // Warn against template literal placeholder syntax in regular strings
+    "no-template-curly-in-string": 1,
+
+    // Warn if return statements do not either always or never specify values
+    "consistent-return": 1,
+
+    // Warn if no return statements in callbacks of array methods
+    "array-callback-return": 1,
+
+    // Requre the use of === and !==
+    "eqeqeq": 2,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    // Disallow the use of alert, confirm, and prompt
+    "no-alert": 2,
+
+    // Disallow the use of arguments.caller or arguments.callee
+    "no-caller": 2,
+
+    // Disallow null comparisons without type-checking operators
+    "no-eq-null": 2,
+
+    // Disallow the use of eval()
+    "no-eval": 2,
+
+    // Warn against extending native types
+    "no-extend-native": 1,
+
+    // Warn against unnecessary calls to .bind()
+    "no-extra-bind": 1,
+
+    // Warn against unnecessary labels    
+    "no-extra-label": 1,
+
+    // Disallow leading or trailing decimal points in numeric literals
+    "no-floating-decimal": 2,
+
+    // Warn against shorthand type conversions
+    "no-implicit-coercion": 1,
+
+    // Warn against function declarations and expressions inside loop statements
+    "no-loop-func": 1,
+
+    // Disallow new operators with the Function object
+    "no-new-func": 2,
+
+    // Warn against new operators with the String, Number, and Boolean objects
+    "no-new-wrappers": 1,
+
+    // Disallow throwing literals as exceptions
+    "no-throw-literal": 2,
+
+    // Require using Error objects as Promise rejection reasons
+    "prefer-promise-reject-errors": 2,
+
+    // Enforce “for” loop update clause moving the counter in the right direction
+    "for-direction": 2,
+
+    // Enforce return statements in getters
+    "getter-return": 2,
+
+    // Disallow await inside of loops
+    "no-await-in-loop": 2,
+
+    // Disallow comparing against -0
+    "no-compare-neg-zero": 2,
+
+    // Warn against catch clause parameters from shadowing variables in the outer scope
+    "no-catch-shadow": 1,
+
+    // Disallow identifiers from shadowing restricted names
+    "no-shadow-restricted-names": 2,
+
+    // Enforce return statements in callbacks of array methods
+    "callback-return": 2,
+
+    // Require error handling in callbacks
+    "handle-callback-err": 2,
+
+    // Warn against string concatenation with __dirname and __filename
+    "no-path-concat": 1,
+
+    // Prefer using arrow functions for callbacks
+    "prefer-arrow-callback": 1,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    //Enforces the use of catch() on un-returned promises
+    "promise/catch-or-return": 2,
+
+    // Warn against nested then() or catch() statements
+    "promise/no-nesting": 1
+  }
+}
diff --git a/quickstarts/uppercase-firestore/functions/index.js b/quickstarts/uppercase-firestore/functions/index.js
index 95a075fee4..85756cbad9 100644
--- a/quickstarts/uppercase-firestore/functions/index.js
+++ b/quickstarts/uppercase-firestore/functions/index.js
@@ -20,7 +20,7 @@
 // The Cloud Functions for Firebase SDK to create Cloud Functions and setup triggers.
 const functions = require('firebase-functions');
 
-// The Firebase Admin SDK to access the Firebase Realtime Database. 
+// The Firebase Admin SDK to access the Firebase Realtime Database.
 const admin = require('firebase-admin');
 admin.initializeApp(functions.config().firebase);
 // [END import]
@@ -35,9 +35,9 @@ exports.addMessage = functions.https.onRequest((req, res) => {
   const original = req.query.text;
   // [START adminSdkAdd]
   // Push the new message into the Realtime Database using the Firebase Admin SDK.
-  admin.firestore().collection('messages').add({original: original}).then(writeResult => {
+  return admin.firestore().collection('messages').add({original: original}).then((writeResult) => {
     // Send back a message that we've succesfully written the message
-    res.json({result: `Message with ID: ${writeResult.id} added.`});
+    return res.json({result: `Message with ID: ${writeResult.id} added.`});
   });
   // [END adminSdkAdd]
 });
@@ -47,20 +47,19 @@ exports.addMessage = functions.https.onRequest((req, res) => {
 // Listens for new messages added to /messages/:documentId/original and creates an
 // uppercase version of the message to /messages/:documentId/uppercase
 // [START makeUppercaseTrigger]
-exports.makeUppercase = functions.firestore.document('/messages/{documentId}')
-    .onCreate(event => {
+exports.makeUppercase = functions.firestore.document('/messages/{documentId}').onCreate((event) => {
 // [END makeUppercaseTrigger]
-      // [START makeUppercaseBody]
+  // [START makeUppercaseBody]
 
-      // Grab the current value of what was written to the Realtime Database.
-      const original = event.data.data().original;
-      console.log('Uppercasing', event.params.documentId, original);
-      const uppercase = original.toUpperCase();
-      // You must return a Promise when performing asynchronous tasks inside a Functions such as
-      // writing to the Firebase Realtime Database.
-      // Setting an 'uppercase' sibling in the Realtime Database returns a Promise.
-      return event.data.ref.set({uppercase}, {merge: true});
-      // [END makeUppercaseBody]
-    });
+  // Grab the current value of what was written to the Realtime Database.
+  const original = event.data.data().original;
+  console.log('Uppercasing', event.params.documentId, original);
+  const uppercase = original.toUpperCase();
+  // You must return a Promise when performing asynchronous tasks inside a Functions such as
+  // writing to the Firebase Realtime Database.
+  // Setting an 'uppercase' sibling in the Realtime Database returns a Promise.
+  return event.data.ref.set({uppercase}, {merge: true});
+  // [END makeUppercaseBody]
+});
 // [END makeUppercase]
 // [END all]
diff --git a/quickstarts/uppercase/functions/.eslintrc.json b/quickstarts/uppercase/functions/.eslintrc.json
new file mode 100644
index 0000000000..eb4c93169b
--- /dev/null
+++ b/quickstarts/uppercase/functions/.eslintrc.json
@@ -0,0 +1,125 @@
+{
+  "parserOptions": {
+    // Required for certain syntax usages
+    "ecmaVersion": 6
+  },
+  "plugins": [
+    "promise"
+  ],
+  "extends": "eslint:recommended",
+  "rules": {
+    // Removed rule "disallow the use of console" from recommended eslint rules
+    "no-console": "off",
+
+    // Removed rule "disallow multiple spaces in regular expressions" from recommended eslint rules
+    "no-regex-spaces": "off",
+
+    // Removed rule "disallow the use of debugger" from recommended eslint rules
+    "no-debugger": "off",
+
+    // Removed rule "disallow unused variables" from recommended eslint rules
+    "no-unused-vars": "off",
+
+    // Removed rule "disallow mixed spaces and tabs for indentation" from recommended eslint rules
+    "no-mixed-spaces-and-tabs": "off",
+
+    // Removed rule "disallow the use of undeclared variables unless mentioned in /*global */ comments" from recommended eslint rules
+    "no-undef": "off",
+
+    // Warn against template literal placeholder syntax in regular strings
+    "no-template-curly-in-string": 1,
+
+    // Warn if return statements do not either always or never specify values
+    "consistent-return": 1,
+
+    // Warn if no return statements in callbacks of array methods
+    "array-callback-return": 1,
+
+    // Requre the use of === and !==
+    "eqeqeq": 2,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    // Disallow the use of alert, confirm, and prompt
+    "no-alert": 2,
+
+    // Disallow the use of arguments.caller or arguments.callee
+    "no-caller": 2,
+
+    // Disallow null comparisons without type-checking operators
+    "no-eq-null": 2,
+
+    // Disallow the use of eval()
+    "no-eval": 2,
+
+    // Warn against extending native types
+    "no-extend-native": 1,
+
+    // Warn against unnecessary calls to .bind()
+    "no-extra-bind": 1,
+
+    // Warn against unnecessary labels    
+    "no-extra-label": 1,
+
+    // Disallow leading or trailing decimal points in numeric literals
+    "no-floating-decimal": 2,
+
+    // Warn against shorthand type conversions
+    "no-implicit-coercion": 1,
+
+    // Warn against function declarations and expressions inside loop statements
+    "no-loop-func": 1,
+
+    // Disallow new operators with the Function object
+    "no-new-func": 2,
+
+    // Warn against new operators with the String, Number, and Boolean objects
+    "no-new-wrappers": 1,
+
+    // Disallow throwing literals as exceptions
+    "no-throw-literal": 2,
+
+    // Require using Error objects as Promise rejection reasons
+    "prefer-promise-reject-errors": 2,
+
+    // Enforce “for” loop update clause moving the counter in the right direction
+    "for-direction": 2,
+
+    // Enforce return statements in getters
+    "getter-return": 2,
+
+    // Disallow await inside of loops
+    "no-await-in-loop": 2,
+
+    // Disallow comparing against -0
+    "no-compare-neg-zero": 2,
+
+    // Warn against catch clause parameters from shadowing variables in the outer scope
+    "no-catch-shadow": 1,
+
+    // Disallow identifiers from shadowing restricted names
+    "no-shadow-restricted-names": 2,
+
+    // Enforce return statements in callbacks of array methods
+    "callback-return": 2,
+
+    // Require error handling in callbacks
+    "handle-callback-err": 2,
+
+    // Warn against string concatenation with __dirname and __filename
+    "no-path-concat": 1,
+
+    // Prefer using arrow functions for callbacks
+    "prefer-arrow-callback": 1,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    //Enforces the use of catch() on un-returned promises
+    "promise/catch-or-return": 2,
+
+    // Warn against nested then() or catch() statements
+    "promise/no-nesting": 1
+  }
+}
diff --git a/quickstarts/uppercase/functions/index.js b/quickstarts/uppercase/functions/index.js
index 94ad65d291..26c3a818b1 100644
--- a/quickstarts/uppercase/functions/index.js
+++ b/quickstarts/uppercase/functions/index.js
@@ -20,7 +20,7 @@
 // The Cloud Functions for Firebase SDK to create Cloud Functions and setup triggers.
 const functions = require('firebase-functions');
 
-// The Firebase Admin SDK to access the Firebase Realtime Database. 
+// The Firebase Admin SDK to access the Firebase Realtime Database.
 const admin = require('firebase-admin');
 admin.initializeApp(functions.config().firebase);
 // [END import]
@@ -35,9 +35,9 @@ exports.addMessage = functions.https.onRequest((req, res) => {
   const original = req.query.text;
   // [START adminSdkPush]
   // Push the new message into the Realtime Database using the Firebase Admin SDK.
-  admin.database().ref('/messages').push({original: original}).then(snapshot => {
+  return admin.database().ref('/messages').push({original: original}).then((snapshot) => {
     // Redirect with 303 SEE OTHER to the URL of the pushed object in the Firebase console.
-    res.redirect(303, snapshot.ref);
+    return res.redirect(303, snapshot.ref);
   });
   // [END adminSdkPush]
 });
@@ -47,19 +47,18 @@ exports.addMessage = functions.https.onRequest((req, res) => {
 // Listens for new messages added to /messages/:pushId/original and creates an
 // uppercase version of the message to /messages/:pushId/uppercase
 // [START makeUppercaseTrigger]
-exports.makeUppercase = functions.database.ref('/messages/{pushId}/original')
-    .onWrite(event => {
+exports.makeUppercase = functions.database.ref('/messages/{pushId}/original').onWrite((event) => {
 // [END makeUppercaseTrigger]
-      // [START makeUppercaseBody]
-      // Grab the current value of what was written to the Realtime Database.
-      const original = event.data.val();
-      console.log('Uppercasing', event.params.pushId, original);
-      const uppercase = original.toUpperCase();
-      // You must return a Promise when performing asynchronous tasks inside a Functions such as
-      // writing to the Firebase Realtime Database.
-      // Setting an "uppercase" sibling in the Realtime Database returns a Promise.
-      return event.data.ref.parent.child('uppercase').set(uppercase);
-      // [END makeUppercaseBody]
-    });
+  // [START makeUppercaseBody]
+  // Grab the current value of what was written to the Realtime Database.
+  const original = event.data.val();
+  console.log('Uppercasing', event.params.pushId, original);
+  const uppercase = original.toUpperCase();
+  // You must return a Promise when performing asynchronous tasks inside a Functions such as
+  // writing to the Firebase Realtime Database.
+  // Setting an "uppercase" sibling in the Realtime Database returns a Promise.
+  return event.data.ref.parent.child('uppercase').set(uppercase);
+  // [END makeUppercaseBody]
+});
 // [END makeUppercase]
 // [END all]
diff --git a/spotify-auth/functions/.eslintrc.json b/spotify-auth/functions/.eslintrc.json
new file mode 100644
index 0000000000..eb4c93169b
--- /dev/null
+++ b/spotify-auth/functions/.eslintrc.json
@@ -0,0 +1,125 @@
+{
+  "parserOptions": {
+    // Required for certain syntax usages
+    "ecmaVersion": 6
+  },
+  "plugins": [
+    "promise"
+  ],
+  "extends": "eslint:recommended",
+  "rules": {
+    // Removed rule "disallow the use of console" from recommended eslint rules
+    "no-console": "off",
+
+    // Removed rule "disallow multiple spaces in regular expressions" from recommended eslint rules
+    "no-regex-spaces": "off",
+
+    // Removed rule "disallow the use of debugger" from recommended eslint rules
+    "no-debugger": "off",
+
+    // Removed rule "disallow unused variables" from recommended eslint rules
+    "no-unused-vars": "off",
+
+    // Removed rule "disallow mixed spaces and tabs for indentation" from recommended eslint rules
+    "no-mixed-spaces-and-tabs": "off",
+
+    // Removed rule "disallow the use of undeclared variables unless mentioned in /*global */ comments" from recommended eslint rules
+    "no-undef": "off",
+
+    // Warn against template literal placeholder syntax in regular strings
+    "no-template-curly-in-string": 1,
+
+    // Warn if return statements do not either always or never specify values
+    "consistent-return": 1,
+
+    // Warn if no return statements in callbacks of array methods
+    "array-callback-return": 1,
+
+    // Requre the use of === and !==
+    "eqeqeq": 2,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    // Disallow the use of alert, confirm, and prompt
+    "no-alert": 2,
+
+    // Disallow the use of arguments.caller or arguments.callee
+    "no-caller": 2,
+
+    // Disallow null comparisons without type-checking operators
+    "no-eq-null": 2,
+
+    // Disallow the use of eval()
+    "no-eval": 2,
+
+    // Warn against extending native types
+    "no-extend-native": 1,
+
+    // Warn against unnecessary calls to .bind()
+    "no-extra-bind": 1,
+
+    // Warn against unnecessary labels    
+    "no-extra-label": 1,
+
+    // Disallow leading or trailing decimal points in numeric literals
+    "no-floating-decimal": 2,
+
+    // Warn against shorthand type conversions
+    "no-implicit-coercion": 1,
+
+    // Warn against function declarations and expressions inside loop statements
+    "no-loop-func": 1,
+
+    // Disallow new operators with the Function object
+    "no-new-func": 2,
+
+    // Warn against new operators with the String, Number, and Boolean objects
+    "no-new-wrappers": 1,
+
+    // Disallow throwing literals as exceptions
+    "no-throw-literal": 2,
+
+    // Require using Error objects as Promise rejection reasons
+    "prefer-promise-reject-errors": 2,
+
+    // Enforce “for” loop update clause moving the counter in the right direction
+    "for-direction": 2,
+
+    // Enforce return statements in getters
+    "getter-return": 2,
+
+    // Disallow await inside of loops
+    "no-await-in-loop": 2,
+
+    // Disallow comparing against -0
+    "no-compare-neg-zero": 2,
+
+    // Warn against catch clause parameters from shadowing variables in the outer scope
+    "no-catch-shadow": 1,
+
+    // Disallow identifiers from shadowing restricted names
+    "no-shadow-restricted-names": 2,
+
+    // Enforce return statements in callbacks of array methods
+    "callback-return": 2,
+
+    // Require error handling in callbacks
+    "handle-callback-err": 2,
+
+    // Warn against string concatenation with __dirname and __filename
+    "no-path-concat": 1,
+
+    // Prefer using arrow functions for callbacks
+    "prefer-arrow-callback": 1,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    //Enforces the use of catch() on un-returned promises
+    "promise/catch-or-return": 2,
+
+    // Warn against nested then() or catch() statements
+    "promise/no-nesting": 1
+  }
+}
diff --git a/spotify-auth/functions/index.js b/spotify-auth/functions/index.js
index 25a6c45ed2..9efe2c6e54 100644
--- a/spotify-auth/functions/index.js
+++ b/spotify-auth/functions/index.js
@@ -24,7 +24,7 @@ const admin = require('firebase-admin');
 const serviceAccount = require('./service-account.json');
 admin.initializeApp({
   credential: admin.credential.cert(serviceAccount),
-  databaseURL: `https://${process.env.GCLOUD_PROJECT}.firebaseio.com`
+  databaseURL: `https://${process.env.GCLOUD_PROJECT}.firebaseio.com`,
 });
 
 // Spotify OAuth 2 setup
@@ -33,7 +33,7 @@ const SpotifyWebApi = require('spotify-web-api-node');
 const Spotify = new SpotifyWebApi({
   clientId: functions.config().spotify.client_id,
   clientSecret: functions.config().spotify.client_secret,
-  redirectUri: `https://${process.env.GCLOUD_PROJECT}.firebaseapp.com/popup.html`
+  redirectUri: `https://${process.env.GCLOUD_PROJECT}.firebaseapp.com/popup.html`,
 });
 
 // Scopes to request.
@@ -76,7 +76,7 @@ exports.token = functions.https.onRequest((req, res) => {
         }
         console.log('Received Access Token:', data.body['access_token']);
         Spotify.setAccessToken(data.body['access_token']);
-        
+
         Spotify.getMe((error, userResults) => {
           if (error) {
             throw error;
@@ -90,10 +90,10 @@ exports.token = functions.https.onRequest((req, res) => {
           const email = userResults.body['email'];
 
           // Create a Firebase account and get the Custom Auth Token.
-          createFirebaseAccount(spotifyUserID, userName, profilePic, email, accessToken).then(
-              firebaseToken => {
+          return createFirebaseAccount(spotifyUserID, userName, profilePic, email, accessToken).then(
+              (firebaseToken) => {
                 // Serve an HTML page that signs the user in and updates the user profile.
-                res.jsonp({token: firebaseToken});
+                return res.jsonp({token: firebaseToken});
               });
         });
       });
@@ -101,6 +101,7 @@ exports.token = functions.https.onRequest((req, res) => {
   } catch (error) {
     return res.jsonp({error: error.toString});
   }
+  return null;
 });
 
 /**
@@ -116,15 +117,15 @@ function createFirebaseAccount(spotifyID, displayName, photoURL, email, accessTo
 
   // Save the access token to the Firebase Realtime Database.
   const databaseTask = admin.database().ref(`/spotifyAccessToken/${uid}`)
-      .set(accessToken);
+  .set(accessToken);
 
   // Create or update the user account.
   const userCreationTask = admin.auth().updateUser(uid, {
     displayName: displayName,
     photoURL: photoURL,
     email: email,
-    emailVerified: true
-  }).catch(error => {
+    emailVerified: true,
+  }).catch((error) => {
     // If user does not exists we create it.
     if (error.code === 'auth/user-not-found') {
       return admin.auth().createUser({
@@ -132,7 +133,7 @@ function createFirebaseAccount(spotifyID, displayName, photoURL, email, accessTo
         displayName: displayName,
         photoURL: photoURL,
         email: email,
-        emailVerified: true
+        emailVerified: true,
       });
     }
     throw error;
@@ -141,9 +142,9 @@ function createFirebaseAccount(spotifyID, displayName, photoURL, email, accessTo
   // Wait for all async tasks to complete, then generate and return a custom auth token.
   return Promise.all([userCreationTask, databaseTask]).then(() => {
     // Create a Firebase custom auth token.
-    return admin.auth().createCustomToken(uid).then((token) => {
-      console.log('Created Custom token for UID "', uid, '" Token:', token);
-      return token;
-    });
+    return admin.auth().createCustomToken(uid);
+  }).then((token) => {
+    console.log('Created Custom token for UID "', uid, '" Token:', token);
+    return token;
   });
 }
diff --git a/stripe/functions/.eslintrc.json b/stripe/functions/.eslintrc.json
new file mode 100644
index 0000000000..eb4c93169b
--- /dev/null
+++ b/stripe/functions/.eslintrc.json
@@ -0,0 +1,125 @@
+{
+  "parserOptions": {
+    // Required for certain syntax usages
+    "ecmaVersion": 6
+  },
+  "plugins": [
+    "promise"
+  ],
+  "extends": "eslint:recommended",
+  "rules": {
+    // Removed rule "disallow the use of console" from recommended eslint rules
+    "no-console": "off",
+
+    // Removed rule "disallow multiple spaces in regular expressions" from recommended eslint rules
+    "no-regex-spaces": "off",
+
+    // Removed rule "disallow the use of debugger" from recommended eslint rules
+    "no-debugger": "off",
+
+    // Removed rule "disallow unused variables" from recommended eslint rules
+    "no-unused-vars": "off",
+
+    // Removed rule "disallow mixed spaces and tabs for indentation" from recommended eslint rules
+    "no-mixed-spaces-and-tabs": "off",
+
+    // Removed rule "disallow the use of undeclared variables unless mentioned in /*global */ comments" from recommended eslint rules
+    "no-undef": "off",
+
+    // Warn against template literal placeholder syntax in regular strings
+    "no-template-curly-in-string": 1,
+
+    // Warn if return statements do not either always or never specify values
+    "consistent-return": 1,
+
+    // Warn if no return statements in callbacks of array methods
+    "array-callback-return": 1,
+
+    // Requre the use of === and !==
+    "eqeqeq": 2,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    // Disallow the use of alert, confirm, and prompt
+    "no-alert": 2,
+
+    // Disallow the use of arguments.caller or arguments.callee
+    "no-caller": 2,
+
+    // Disallow null comparisons without type-checking operators
+    "no-eq-null": 2,
+
+    // Disallow the use of eval()
+    "no-eval": 2,
+
+    // Warn against extending native types
+    "no-extend-native": 1,
+
+    // Warn against unnecessary calls to .bind()
+    "no-extra-bind": 1,
+
+    // Warn against unnecessary labels    
+    "no-extra-label": 1,
+
+    // Disallow leading or trailing decimal points in numeric literals
+    "no-floating-decimal": 2,
+
+    // Warn against shorthand type conversions
+    "no-implicit-coercion": 1,
+
+    // Warn against function declarations and expressions inside loop statements
+    "no-loop-func": 1,
+
+    // Disallow new operators with the Function object
+    "no-new-func": 2,
+
+    // Warn against new operators with the String, Number, and Boolean objects
+    "no-new-wrappers": 1,
+
+    // Disallow throwing literals as exceptions
+    "no-throw-literal": 2,
+
+    // Require using Error objects as Promise rejection reasons
+    "prefer-promise-reject-errors": 2,
+
+    // Enforce “for” loop update clause moving the counter in the right direction
+    "for-direction": 2,
+
+    // Enforce return statements in getters
+    "getter-return": 2,
+
+    // Disallow await inside of loops
+    "no-await-in-loop": 2,
+
+    // Disallow comparing against -0
+    "no-compare-neg-zero": 2,
+
+    // Warn against catch clause parameters from shadowing variables in the outer scope
+    "no-catch-shadow": 1,
+
+    // Disallow identifiers from shadowing restricted names
+    "no-shadow-restricted-names": 2,
+
+    // Enforce return statements in callbacks of array methods
+    "callback-return": 2,
+
+    // Require error handling in callbacks
+    "handle-callback-err": 2,
+
+    // Warn against string concatenation with __dirname and __filename
+    "no-path-concat": 1,
+
+    // Prefer using arrow functions for callbacks
+    "prefer-arrow-callback": 1,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    //Enforces the use of catch() on un-returned promises
+    "promise/catch-or-return": 2,
+
+    // Warn against nested then() or catch() statements
+    "promise/no-nesting": 1
+  }
+}
diff --git a/stripe/functions/index.js b/stripe/functions/index.js
index 6af9e2c1a5..7fe5fd521c 100644
--- a/stripe/functions/index.js
+++ b/stripe/functions/index.js
@@ -15,78 +15,77 @@
  */
 'use strict';
 
-const functions = require('firebase-functions'),
-      admin = require('firebase-admin'),
-      logging = require('@google-cloud/logging')();
+const functions = require('firebase-functions');
+const admin = require('firebase-admin');
+const logging = require('@google-cloud/logging')();
 
 admin.initializeApp(functions.config().firebase);
 
-const stripe = require('stripe')(functions.config().stripe.token),
-      currency = functions.config().stripe.currency || 'USD';
+const stripe = require('stripe')(functions.config().stripe.token);
+const currency = functions.config().stripe.currency || 'USD';
 
 // [START chargecustomer]
 // Charge the Stripe customer whenever an amount is written to the Realtime database
-exports.createStripeCharge = functions.database.ref('/stripe_customers/{userId}/charges/{id}').onWrite(event => {
+exports.createStripeCharge = functions.database.ref('/stripe_customers/{userId}/charges/{id}').onWrite((event) => {
   const val = event.data.val();
   // This onWrite will trigger whenever anything is written to the path, so
-  // noop if the charge was deleted, errored out, or the Stripe API returned a result (id exists) 
+  // noop if the charge was deleted, errored out, or the Stripe API returned a result (id exists)
   if (val === null || val.id || val.error) return null;
   // Look up the Stripe customer id written in createStripeCustomer
-  return admin.database().ref(`/stripe_customers/${event.params.userId}/customer_id`).once('value').then(snapshot => {
+  return admin.database().ref(`/stripe_customers/${event.params.userId}/customer_id`).once('value').then((snapshot) => {
     return snapshot.val();
-  }).then(customer => {
-    // Create a charge using the pushId as the idempotency key, protecting against double charges 
+  }).then((customer) => {
+    // Create a charge using the pushId as the idempotency key, protecting against double charges
     const amount = val.amount;
     const idempotency_key = event.params.id;
     let charge = {amount, currency, customer};
     if (val.source !== null) charge.source = val.source;
     return stripe.charges.create(charge, {idempotency_key});
-  }).then(response => {
-      // If the result is successful, write it back to the database
-      return event.data.adminRef.set(response);
-    }, error => {
-      // We want to capture errors and render them in a user-friendly way, while
-      // still logging an exception with Stackdriver
-      return event.data.adminRef.child('error').set(userFacingMessage(error)).then(() => {
-        return reportError(error, {user: event.params.userId});
-      });
-    }
-  );
+  }).then((response) => {
+    // If the result is successful, write it back to the database
+    return event.data.adminRef.set(response);
+  }).catch((error) => {
+    // We want to capture errors and render them in a user-friendly way, while
+    // still logging an exception with Stackdriver
+    return event.data.adminRef.child('error').set(userFacingMessage(error));
+  }).then(() => {
+    return reportError(error, {user: event.params.userId});
+  });
 });
 // [END chargecustomer]]
 
 // When a user is created, register them with Stripe
-exports.createStripeCustomer = functions.auth.user().onCreate(event => {
+exports.createStripeCustomer = functions.auth.user().onCreate((event) => {
   const data = event.data;
   return stripe.customers.create({
-    email: data.email
-  }).then(customer => {
+    email: data.email,
+  }).then((customer) => {
     return admin.database().ref(`/stripe_customers/${data.uid}/customer_id`).set(customer.id);
   });
 });
 
 // Add a payment source (card) for a user by writing a stripe payment source token to Realtime database
-exports.addPaymentSource = functions.database.ref('/stripe_customers/{userId}/sources/{pushId}/token').onWrite(event => {
+exports.addPaymentSource = functions.database.ref('/stripe_customers/{userId}/sources/{pushId}/token').onWrite((event) => {
   const source = event.data.val();
   if (source === null) return null;
-  return admin.database().ref(`/stripe_customers/${event.params.userId}/customer_id`).once('value').then(snapshot => {
+  return admin.database().ref(`/stripe_customers/${event.params.userId}/customer_id`).once('value').then((snapshot) => {
     return snapshot.val();
-  }).then(customer => {
+  }).then((customer) => {
     return stripe.customers.createSource(customer, {source});
-  }).then(response => {
-      return event.data.adminRef.parent.set(response);
-    }, error => {
-      return event.data.adminRef.parent.child('error').set(userFacingMessage(error)).then(() => {
-        return reportError(error, {user: event.params.userId});
-      });
+  }).then((response) => {
+    return event.data.adminRef.parent.set(response);
+  }, (error) => {
+    return event.data.adminRef.parent.child('error').set(userFacingMessage(error));
+  }).then(() => {
+    return reportError(error, {user: event.params.userId});
   });
 });
 
 // When a user deletes their account, clean up after them
-exports.cleanupUser = functions.auth.user().onDelete(event => {
-  return admin.database().ref(`/stripe_customers/${event.data.uid}`).once('value').then(snapshot => {
+exports.cleanupUser = functions.auth.user().onDelete((event) => {
+  return admin.database().ref(`/stripe_customers/${event.data.uid}`).once('value').then((snapshot) => {
     return snapshot.val();
-  }).then(customer => {
+  }).then((customer) => {
     return stripe.customers.del(customer.customer_id);
   }).then(() => {
     return admin.database().ref(`/stripe_customers/${event.data.uid}`).remove();
@@ -108,8 +107,8 @@ function reportError(err, context = {}) {
   const metadata = {
     resource: {
       type: 'cloud_function',
-      labels: { function_name: process.env.FUNCTION_NAME }
-    }
+      labels: {function_name: process.env.FUNCTION_NAME},
+    },
   };
 
   // https://cloud.google.com/error-reporting/reference/rest/v1beta1/ErrorEvent
@@ -117,15 +116,17 @@ function reportError(err, context = {}) {
     message: err.stack,
     serviceContext: {
       service: process.env.FUNCTION_NAME,
-      resourceType: 'cloud_function'
+      resourceType: 'cloud_function',
     },
-    context: context
+    context: context,
   };
 
   // Write the error log entry
   return new Promise((resolve, reject) => {
-    log.write(log.entry(metadata, errorEvent), error => {
-      if (error) { reject(error); }
+    log.write(log.entry(metadata, errorEvent), (error) => {
+      if (error) {
+ reject(error);
+}
       resolve();
     });
   });
diff --git a/survey-app-update/functions/.eslintrc.json b/survey-app-update/functions/.eslintrc.json
new file mode 100644
index 0000000000..eb4c93169b
--- /dev/null
+++ b/survey-app-update/functions/.eslintrc.json
@@ -0,0 +1,125 @@
+{
+  "parserOptions": {
+    // Required for certain syntax usages
+    "ecmaVersion": 6
+  },
+  "plugins": [
+    "promise"
+  ],
+  "extends": "eslint:recommended",
+  "rules": {
+    // Removed rule "disallow the use of console" from recommended eslint rules
+    "no-console": "off",
+
+    // Removed rule "disallow multiple spaces in regular expressions" from recommended eslint rules
+    "no-regex-spaces": "off",
+
+    // Removed rule "disallow the use of debugger" from recommended eslint rules
+    "no-debugger": "off",
+
+    // Removed rule "disallow unused variables" from recommended eslint rules
+    "no-unused-vars": "off",
+
+    // Removed rule "disallow mixed spaces and tabs for indentation" from recommended eslint rules
+    "no-mixed-spaces-and-tabs": "off",
+
+    // Removed rule "disallow the use of undeclared variables unless mentioned in /*global */ comments" from recommended eslint rules
+    "no-undef": "off",
+
+    // Warn against template literal placeholder syntax in regular strings
+    "no-template-curly-in-string": 1,
+
+    // Warn if return statements do not either always or never specify values
+    "consistent-return": 1,
+
+    // Warn if no return statements in callbacks of array methods
+    "array-callback-return": 1,
+
+    // Requre the use of === and !==
+    "eqeqeq": 2,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    // Disallow the use of alert, confirm, and prompt
+    "no-alert": 2,
+
+    // Disallow the use of arguments.caller or arguments.callee
+    "no-caller": 2,
+
+    // Disallow null comparisons without type-checking operators
+    "no-eq-null": 2,
+
+    // Disallow the use of eval()
+    "no-eval": 2,
+
+    // Warn against extending native types
+    "no-extend-native": 1,
+
+    // Warn against unnecessary calls to .bind()
+    "no-extra-bind": 1,
+
+    // Warn against unnecessary labels    
+    "no-extra-label": 1,
+
+    // Disallow leading or trailing decimal points in numeric literals
+    "no-floating-decimal": 2,
+
+    // Warn against shorthand type conversions
+    "no-implicit-coercion": 1,
+
+    // Warn against function declarations and expressions inside loop statements
+    "no-loop-func": 1,
+
+    // Disallow new operators with the Function object
+    "no-new-func": 2,
+
+    // Warn against new operators with the String, Number, and Boolean objects
+    "no-new-wrappers": 1,
+
+    // Disallow throwing literals as exceptions
+    "no-throw-literal": 2,
+
+    // Require using Error objects as Promise rejection reasons
+    "prefer-promise-reject-errors": 2,
+
+    // Enforce “for” loop update clause moving the counter in the right direction
+    "for-direction": 2,
+
+    // Enforce return statements in getters
+    "getter-return": 2,
+
+    // Disallow await inside of loops
+    "no-await-in-loop": 2,
+
+    // Disallow comparing against -0
+    "no-compare-neg-zero": 2,
+
+    // Warn against catch clause parameters from shadowing variables in the outer scope
+    "no-catch-shadow": 1,
+
+    // Disallow identifiers from shadowing restricted names
+    "no-shadow-restricted-names": 2,
+
+    // Enforce return statements in callbacks of array methods
+    "callback-return": 2,
+
+    // Require error handling in callbacks
+    "handle-callback-err": 2,
+
+    // Warn against string concatenation with __dirname and __filename
+    "no-path-concat": 1,
+
+    // Prefer using arrow functions for callbacks
+    "prefer-arrow-callback": 1,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    //Enforces the use of catch() on un-returned promises
+    "promise/catch-or-return": 2,
+
+    // Warn against nested then() or catch() statements
+    "promise/no-nesting": 1
+  }
+}
diff --git a/survey-app-update/functions/index.js b/survey-app-update/functions/index.js
index a9d8c12513..8a7bc37452 100644
--- a/survey-app-update/functions/index.js
+++ b/survey-app-update/functions/index.js
@@ -34,7 +34,7 @@ const LATEST_VERSION = '2.0';
 /**
  * After a user has updated the app. Send them a survey to compare the app with the old version.
  */
-exports.sendAppUpdateSurvey = functions.analytics.event('app_update').onLog(event => {
+exports.sendAppUpdateSurvey = functions.analytics.event('app_update').onLog((event) => {
   const uid = event.data.user.userId;
   const appVerion = event.data.user.appInfo.appVersion;
 
@@ -43,12 +43,13 @@ exports.sendAppUpdateSurvey = functions.analytics.event('app_update').onLog(even
     // Fetch the email of the user. In this sample we assume that the app is using Firebase Auth and
     // has set the Firebase Analytics User ID to be the same as the Firebase Auth uid using the
     // setUserId API.
-    return admin.auth().getUser(uid).then(user => {
+    return admin.auth().getUser(uid).then((user) => {
       const email = user.email;
       const name = user.displayName;
       return sendSurveyEmail(email, name);
     });
   }
+  return null;
 });
 
 /**
@@ -61,10 +62,10 @@ function sendSurveyEmail(email, name) {
     subject: 'How did you like our new app?',
     text: `Hey ${name}, We've seen that you have upgraded to the new version of our app!
            It would be awesome if you could tell us how you like it.
-           Fill out our survey: ${LINK_TO_SURVEY}`
+           Fill out our survey: ${LINK_TO_SURVEY}`,
   };
 
   return mailTransport.sendMail(mailOptions).then(() => {
-    console.log('Upgrade App Survey email sent to:', email);
+    return console.log('Upgrade App Survey email sent to:', email);
   });
 }
diff --git a/template-handlebars/functions/.eslintrc.json b/template-handlebars/functions/.eslintrc.json
new file mode 100644
index 0000000000..eb4c93169b
--- /dev/null
+++ b/template-handlebars/functions/.eslintrc.json
@@ -0,0 +1,125 @@
+{
+  "parserOptions": {
+    // Required for certain syntax usages
+    "ecmaVersion": 6
+  },
+  "plugins": [
+    "promise"
+  ],
+  "extends": "eslint:recommended",
+  "rules": {
+    // Removed rule "disallow the use of console" from recommended eslint rules
+    "no-console": "off",
+
+    // Removed rule "disallow multiple spaces in regular expressions" from recommended eslint rules
+    "no-regex-spaces": "off",
+
+    // Removed rule "disallow the use of debugger" from recommended eslint rules
+    "no-debugger": "off",
+
+    // Removed rule "disallow unused variables" from recommended eslint rules
+    "no-unused-vars": "off",
+
+    // Removed rule "disallow mixed spaces and tabs for indentation" from recommended eslint rules
+    "no-mixed-spaces-and-tabs": "off",
+
+    // Removed rule "disallow the use of undeclared variables unless mentioned in /*global */ comments" from recommended eslint rules
+    "no-undef": "off",
+
+    // Warn against template literal placeholder syntax in regular strings
+    "no-template-curly-in-string": 1,
+
+    // Warn if return statements do not either always or never specify values
+    "consistent-return": 1,
+
+    // Warn if no return statements in callbacks of array methods
+    "array-callback-return": 1,
+
+    // Requre the use of === and !==
+    "eqeqeq": 2,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    // Disallow the use of alert, confirm, and prompt
+    "no-alert": 2,
+
+    // Disallow the use of arguments.caller or arguments.callee
+    "no-caller": 2,
+
+    // Disallow null comparisons without type-checking operators
+    "no-eq-null": 2,
+
+    // Disallow the use of eval()
+    "no-eval": 2,
+
+    // Warn against extending native types
+    "no-extend-native": 1,
+
+    // Warn against unnecessary calls to .bind()
+    "no-extra-bind": 1,
+
+    // Warn against unnecessary labels    
+    "no-extra-label": 1,
+
+    // Disallow leading or trailing decimal points in numeric literals
+    "no-floating-decimal": 2,
+
+    // Warn against shorthand type conversions
+    "no-implicit-coercion": 1,
+
+    // Warn against function declarations and expressions inside loop statements
+    "no-loop-func": 1,
+
+    // Disallow new operators with the Function object
+    "no-new-func": 2,
+
+    // Warn against new operators with the String, Number, and Boolean objects
+    "no-new-wrappers": 1,
+
+    // Disallow throwing literals as exceptions
+    "no-throw-literal": 2,
+
+    // Require using Error objects as Promise rejection reasons
+    "prefer-promise-reject-errors": 2,
+
+    // Enforce “for” loop update clause moving the counter in the right direction
+    "for-direction": 2,
+
+    // Enforce return statements in getters
+    "getter-return": 2,
+
+    // Disallow await inside of loops
+    "no-await-in-loop": 2,
+
+    // Disallow comparing against -0
+    "no-compare-neg-zero": 2,
+
+    // Warn against catch clause parameters from shadowing variables in the outer scope
+    "no-catch-shadow": 1,
+
+    // Disallow identifiers from shadowing restricted names
+    "no-shadow-restricted-names": 2,
+
+    // Enforce return statements in callbacks of array methods
+    "callback-return": 2,
+
+    // Require error handling in callbacks
+    "handle-callback-err": 2,
+
+    // Warn against string concatenation with __dirname and __filename
+    "no-path-concat": 1,
+
+    // Prefer using arrow functions for callbacks
+    "prefer-arrow-callback": 1,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    //Enforces the use of catch() on un-returned promises
+    "promise/catch-or-return": 2,
+
+    // Warn against nested then() or catch() statements
+    "promise/no-nesting": 1
+  }
+}
diff --git a/template-handlebars/functions/firebaseUser.js b/template-handlebars/functions/firebaseUser.js
index 494f1a64f0..18094028fd 100644
--- a/template-handlebars/functions/firebaseUser.js
+++ b/template-handlebars/functions/firebaseUser.js
@@ -26,14 +26,13 @@ const cookieParser = require('cookie-parser')();
 const validateFirebaseIdToken = (req, res, next) => {
   console.log('Check if request is authorized with Firebase ID token');
 
-  getIdTokenFromRequest(req, res).then(idToken => {
+  return getIdTokenFromRequest(req, res).then(idToken => {
     if (idToken) {
-      addDecodedIdTokenToRequest(idToken, req).then(() => {
-        next();
-      });
-    } else {
-      next();
+      return addDecodedIdTokenToRequest(idToken, req);
     }
+    return next();
+  }).then(() => {
+    return next();
   });
 };
 
@@ -46,7 +45,7 @@ function getIdTokenFromRequest(req, res) {
     // Read the ID Token from the Authorization header.
     return Promise.resolve(req.headers.authorization.split('Bearer ')[1]);
   }
-  return new Promise(function(resolve) {
+  return new Promise((resolve, reject) => {
     cookieParser(req, res, () => {
       if (req.cookies && req.cookies.__session) {
         console.log('Found "__session" cookie');
@@ -64,11 +63,11 @@ function getIdTokenFromRequest(req, res) {
  */
 function addDecodedIdTokenToRequest(idToken, req) {
   return admin.auth().verifyIdToken(idToken).then(decodedIdToken => {
-    console.log('ID Token correctly decoded', decodedIdToken);
     req.user = decodedIdToken;
+    return console.log('ID Token correctly decoded', decodedIdToken);
   }).catch(error => {
     console.error('Error while verifying Firebase ID token:', error);
   });
 }
 
-exports.validateFirebaseIdToken = validateFirebaseIdToken;
+exports.validateFirebaseIdToken = validateFirebaseIdToken;
\ No newline at end of file
diff --git a/template-handlebars/functions/index.js b/template-handlebars/functions/index.js
index ef2bab6384..4b9b4e36b8 100644
--- a/template-handlebars/functions/index.js
+++ b/template-handlebars/functions/index.js
@@ -18,6 +18,7 @@
 const functions = require('firebase-functions');
 const admin = require('firebase-admin');
 admin.initializeApp(functions.config().firebase);
+
 const express = require('express');
 const exphbs = require('express-handlebars');
 const app = express();
@@ -29,8 +30,8 @@ app.use(firebaseUser.validateFirebaseIdToken);
 
 app.get('/', (req, res) => {
   console.log('Signed-in user:', req.user);
-  res.render('user', {
-    user: req.user
+  return res.render('user', {
+    user: req.user,
   });
 });
 
diff --git a/text-moderation/functions/.eslintrc.json b/text-moderation/functions/.eslintrc.json
new file mode 100644
index 0000000000..eb4c93169b
--- /dev/null
+++ b/text-moderation/functions/.eslintrc.json
@@ -0,0 +1,125 @@
+{
+  "parserOptions": {
+    // Required for certain syntax usages
+    "ecmaVersion": 6
+  },
+  "plugins": [
+    "promise"
+  ],
+  "extends": "eslint:recommended",
+  "rules": {
+    // Removed rule "disallow the use of console" from recommended eslint rules
+    "no-console": "off",
+
+    // Removed rule "disallow multiple spaces in regular expressions" from recommended eslint rules
+    "no-regex-spaces": "off",
+
+    // Removed rule "disallow the use of debugger" from recommended eslint rules
+    "no-debugger": "off",
+
+    // Removed rule "disallow unused variables" from recommended eslint rules
+    "no-unused-vars": "off",
+
+    // Removed rule "disallow mixed spaces and tabs for indentation" from recommended eslint rules
+    "no-mixed-spaces-and-tabs": "off",
+
+    // Removed rule "disallow the use of undeclared variables unless mentioned in /*global */ comments" from recommended eslint rules
+    "no-undef": "off",
+
+    // Warn against template literal placeholder syntax in regular strings
+    "no-template-curly-in-string": 1,
+
+    // Warn if return statements do not either always or never specify values
+    "consistent-return": 1,
+
+    // Warn if no return statements in callbacks of array methods
+    "array-callback-return": 1,
+
+    // Requre the use of === and !==
+    "eqeqeq": 2,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    // Disallow the use of alert, confirm, and prompt
+    "no-alert": 2,
+
+    // Disallow the use of arguments.caller or arguments.callee
+    "no-caller": 2,
+
+    // Disallow null comparisons without type-checking operators
+    "no-eq-null": 2,
+
+    // Disallow the use of eval()
+    "no-eval": 2,
+
+    // Warn against extending native types
+    "no-extend-native": 1,
+
+    // Warn against unnecessary calls to .bind()
+    "no-extra-bind": 1,
+
+    // Warn against unnecessary labels    
+    "no-extra-label": 1,
+
+    // Disallow leading or trailing decimal points in numeric literals
+    "no-floating-decimal": 2,
+
+    // Warn against shorthand type conversions
+    "no-implicit-coercion": 1,
+
+    // Warn against function declarations and expressions inside loop statements
+    "no-loop-func": 1,
+
+    // Disallow new operators with the Function object
+    "no-new-func": 2,
+
+    // Warn against new operators with the String, Number, and Boolean objects
+    "no-new-wrappers": 1,
+
+    // Disallow throwing literals as exceptions
+    "no-throw-literal": 2,
+
+    // Require using Error objects as Promise rejection reasons
+    "prefer-promise-reject-errors": 2,
+
+    // Enforce “for” loop update clause moving the counter in the right direction
+    "for-direction": 2,
+
+    // Enforce return statements in getters
+    "getter-return": 2,
+
+    // Disallow await inside of loops
+    "no-await-in-loop": 2,
+
+    // Disallow comparing against -0
+    "no-compare-neg-zero": 2,
+
+    // Warn against catch clause parameters from shadowing variables in the outer scope
+    "no-catch-shadow": 1,
+
+    // Disallow identifiers from shadowing restricted names
+    "no-shadow-restricted-names": 2,
+
+    // Enforce return statements in callbacks of array methods
+    "callback-return": 2,
+
+    // Require error handling in callbacks
+    "handle-callback-err": 2,
+
+    // Warn against string concatenation with __dirname and __filename
+    "no-path-concat": 1,
+
+    // Prefer using arrow functions for callbacks
+    "prefer-arrow-callback": 1,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    //Enforces the use of catch() on un-returned promises
+    "promise/catch-or-return": 2,
+
+    // Warn against nested then() or catch() statements
+    "promise/no-nesting": 1
+  }
+}
diff --git a/text-moderation/functions/index.js b/text-moderation/functions/index.js
index 3446ae2ae7..1d54324e93 100644
--- a/text-moderation/functions/index.js
+++ b/text-moderation/functions/index.js
@@ -21,26 +21,26 @@ const Filter = require('bad-words');
 const badWordsFilter = new Filter();
 
 // Moderates messages by lowering all uppercase messages and removing swearwords.
-exports.moderator = functions.database
-    .ref('/messages/{messageId}').onWrite(event => {
-      const message = event.data.val();
+exports.moderator = functions.database.ref('/messages/{messageId}').onWrite((event) => {
+  const message = event.data.val();
 
-      if (message && !message.sanitized) {
-        // Retrieved the message values.
-        console.log('Retrieved message content: ', message);
+  if (message && !message.sanitized) {
+    // Retrieved the message values.
+    console.log('Retrieved message content: ', message);
 
-        // Run moderation checks on on the message and moderate if needed.
-        const moderatedMessage = moderateMessage(message.text);
+    // Run moderation checks on on the message and moderate if needed.
+    const moderatedMessage = moderateMessage(message.text);
 
-        // Update the Firebase DB with checked message.
-        console.log('Message has been moderated. Saving to DB: ', moderatedMessage);
-        return event.data.adminRef.update({
-          text: moderatedMessage,
-          sanitized: true,
-          moderated: message.text !== moderatedMessage
-        });
-      }
+    // Update the Firebase DB with checked message.
+    console.log('Message has been moderated. Saving to DB: ', moderatedMessage);
+    return event.data.adminRef.update({
+      text: moderatedMessage,
+      sanitized: true,
+      moderated: message.text !== moderatedMessage,
     });
+  }
+  return null;
+});
 
 // Moderates the given message if appropriate.
 function moderateMessage(message) {
diff --git a/typescript-getting-started/functions/.eslintrc.json b/typescript-getting-started/functions/.eslintrc.json
new file mode 100644
index 0000000000..eb4c93169b
--- /dev/null
+++ b/typescript-getting-started/functions/.eslintrc.json
@@ -0,0 +1,125 @@
+{
+  "parserOptions": {
+    // Required for certain syntax usages
+    "ecmaVersion": 6
+  },
+  "plugins": [
+    "promise"
+  ],
+  "extends": "eslint:recommended",
+  "rules": {
+    // Removed rule "disallow the use of console" from recommended eslint rules
+    "no-console": "off",
+
+    // Removed rule "disallow multiple spaces in regular expressions" from recommended eslint rules
+    "no-regex-spaces": "off",
+
+    // Removed rule "disallow the use of debugger" from recommended eslint rules
+    "no-debugger": "off",
+
+    // Removed rule "disallow unused variables" from recommended eslint rules
+    "no-unused-vars": "off",
+
+    // Removed rule "disallow mixed spaces and tabs for indentation" from recommended eslint rules
+    "no-mixed-spaces-and-tabs": "off",
+
+    // Removed rule "disallow the use of undeclared variables unless mentioned in /*global */ comments" from recommended eslint rules
+    "no-undef": "off",
+
+    // Warn against template literal placeholder syntax in regular strings
+    "no-template-curly-in-string": 1,
+
+    // Warn if return statements do not either always or never specify values
+    "consistent-return": 1,
+
+    // Warn if no return statements in callbacks of array methods
+    "array-callback-return": 1,
+
+    // Requre the use of === and !==
+    "eqeqeq": 2,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    // Disallow the use of alert, confirm, and prompt
+    "no-alert": 2,
+
+    // Disallow the use of arguments.caller or arguments.callee
+    "no-caller": 2,
+
+    // Disallow null comparisons without type-checking operators
+    "no-eq-null": 2,
+
+    // Disallow the use of eval()
+    "no-eval": 2,
+
+    // Warn against extending native types
+    "no-extend-native": 1,
+
+    // Warn against unnecessary calls to .bind()
+    "no-extra-bind": 1,
+
+    // Warn against unnecessary labels    
+    "no-extra-label": 1,
+
+    // Disallow leading or trailing decimal points in numeric literals
+    "no-floating-decimal": 2,
+
+    // Warn against shorthand type conversions
+    "no-implicit-coercion": 1,
+
+    // Warn against function declarations and expressions inside loop statements
+    "no-loop-func": 1,
+
+    // Disallow new operators with the Function object
+    "no-new-func": 2,
+
+    // Warn against new operators with the String, Number, and Boolean objects
+    "no-new-wrappers": 1,
+
+    // Disallow throwing literals as exceptions
+    "no-throw-literal": 2,
+
+    // Require using Error objects as Promise rejection reasons
+    "prefer-promise-reject-errors": 2,
+
+    // Enforce “for” loop update clause moving the counter in the right direction
+    "for-direction": 2,
+
+    // Enforce return statements in getters
+    "getter-return": 2,
+
+    // Disallow await inside of loops
+    "no-await-in-loop": 2,
+
+    // Disallow comparing against -0
+    "no-compare-neg-zero": 2,
+
+    // Warn against catch clause parameters from shadowing variables in the outer scope
+    "no-catch-shadow": 1,
+
+    // Disallow identifiers from shadowing restricted names
+    "no-shadow-restricted-names": 2,
+
+    // Enforce return statements in callbacks of array methods
+    "callback-return": 2,
+
+    // Require error handling in callbacks
+    "handle-callback-err": 2,
+
+    // Warn against string concatenation with __dirname and __filename
+    "no-path-concat": 1,
+
+    // Prefer using arrow functions for callbacks
+    "prefer-arrow-callback": 1,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    //Enforces the use of catch() on un-returned promises
+    "promise/catch-or-return": 2,
+
+    // Warn against nested then() or catch() statements
+    "promise/no-nesting": 1
+  }
+}
diff --git a/url-shortener/functions/.eslintrc.json b/url-shortener/functions/.eslintrc.json
new file mode 100644
index 0000000000..eb4c93169b
--- /dev/null
+++ b/url-shortener/functions/.eslintrc.json
@@ -0,0 +1,125 @@
+{
+  "parserOptions": {
+    // Required for certain syntax usages
+    "ecmaVersion": 6
+  },
+  "plugins": [
+    "promise"
+  ],
+  "extends": "eslint:recommended",
+  "rules": {
+    // Removed rule "disallow the use of console" from recommended eslint rules
+    "no-console": "off",
+
+    // Removed rule "disallow multiple spaces in regular expressions" from recommended eslint rules
+    "no-regex-spaces": "off",
+
+    // Removed rule "disallow the use of debugger" from recommended eslint rules
+    "no-debugger": "off",
+
+    // Removed rule "disallow unused variables" from recommended eslint rules
+    "no-unused-vars": "off",
+
+    // Removed rule "disallow mixed spaces and tabs for indentation" from recommended eslint rules
+    "no-mixed-spaces-and-tabs": "off",
+
+    // Removed rule "disallow the use of undeclared variables unless mentioned in /*global */ comments" from recommended eslint rules
+    "no-undef": "off",
+
+    // Warn against template literal placeholder syntax in regular strings
+    "no-template-curly-in-string": 1,
+
+    // Warn if return statements do not either always or never specify values
+    "consistent-return": 1,
+
+    // Warn if no return statements in callbacks of array methods
+    "array-callback-return": 1,
+
+    // Requre the use of === and !==
+    "eqeqeq": 2,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    // Disallow the use of alert, confirm, and prompt
+    "no-alert": 2,
+
+    // Disallow the use of arguments.caller or arguments.callee
+    "no-caller": 2,
+
+    // Disallow null comparisons without type-checking operators
+    "no-eq-null": 2,
+
+    // Disallow the use of eval()
+    "no-eval": 2,
+
+    // Warn against extending native types
+    "no-extend-native": 1,
+
+    // Warn against unnecessary calls to .bind()
+    "no-extra-bind": 1,
+
+    // Warn against unnecessary labels    
+    "no-extra-label": 1,
+
+    // Disallow leading or trailing decimal points in numeric literals
+    "no-floating-decimal": 2,
+
+    // Warn against shorthand type conversions
+    "no-implicit-coercion": 1,
+
+    // Warn against function declarations and expressions inside loop statements
+    "no-loop-func": 1,
+
+    // Disallow new operators with the Function object
+    "no-new-func": 2,
+
+    // Warn against new operators with the String, Number, and Boolean objects
+    "no-new-wrappers": 1,
+
+    // Disallow throwing literals as exceptions
+    "no-throw-literal": 2,
+
+    // Require using Error objects as Promise rejection reasons
+    "prefer-promise-reject-errors": 2,
+
+    // Enforce “for” loop update clause moving the counter in the right direction
+    "for-direction": 2,
+
+    // Enforce return statements in getters
+    "getter-return": 2,
+
+    // Disallow await inside of loops
+    "no-await-in-loop": 2,
+
+    // Disallow comparing against -0
+    "no-compare-neg-zero": 2,
+
+    // Warn against catch clause parameters from shadowing variables in the outer scope
+    "no-catch-shadow": 1,
+
+    // Disallow identifiers from shadowing restricted names
+    "no-shadow-restricted-names": 2,
+
+    // Enforce return statements in callbacks of array methods
+    "callback-return": 2,
+
+    // Require error handling in callbacks
+    "handle-callback-err": 2,
+
+    // Warn against string concatenation with __dirname and __filename
+    "no-path-concat": 1,
+
+    // Prefer using arrow functions for callbacks
+    "prefer-arrow-callback": 1,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    //Enforces the use of catch() on un-returned promises
+    "promise/catch-or-return": 2,
+
+    // Warn against nested then() or catch() statements
+    "promise/no-nesting": 1
+  }
+}
diff --git a/url-shortener/functions/index.js b/url-shortener/functions/index.js
index dfe0ffc433..ce50182771 100644
--- a/url-shortener/functions/index.js
+++ b/url-shortener/functions/index.js
@@ -21,10 +21,10 @@ admin.initializeApp(functions.config().firebase);
 const request = require('request-promise');
 
 // Shorten URL
-exports.shortenUrl = functions.database.ref('/links/{linkID}').onWrite(event => {
+exports.shortenUrl = functions.database.ref('/links/{linkID}').onWrite((event) => {
   const snapshot = event.data;
   if (typeof snapshot.val() !== 'string') {
-    return;
+    return null;
   }
   return createShortenerPromise(snapshot);
 });
@@ -35,25 +35,25 @@ function createShortenerRequest(sourceUrl) {
     method: 'POST',
     uri: `https://www.googleapis.com/urlshortener/v1/url?key=${functions.config().firebase.apiKey}`,
     body: {
-      longUrl: sourceUrl
+      longUrl: sourceUrl,
     },
     json: true,
-    resolveWithFullResponse: true
+    resolveWithFullResponse: true,
   };
 }
 
 function createShortenerPromise(snapshot) {
   const key = snapshot.key;
   const originalUrl = snapshot.val();
-  return request(createShortenerRequest(originalUrl)).then(response => {
+  return request(createShortenerRequest(originalUrl)).then((response) => {
     if (response.statusCode === 200) {
       return response.body.id;
     }
     throw response.body;
-  }).then(shortUrl => {
+  }).then((shortUrl) => {
     return admin.database().ref(`/links/${key}`).set({
       original: originalUrl,
-      short: shortUrl
+      short: shortUrl,
     });
   });
 }
diff --git a/username-password-auth/functions/.eslintrc.json b/username-password-auth/functions/.eslintrc.json
new file mode 100644
index 0000000000..eb4c93169b
--- /dev/null
+++ b/username-password-auth/functions/.eslintrc.json
@@ -0,0 +1,125 @@
+{
+  "parserOptions": {
+    // Required for certain syntax usages
+    "ecmaVersion": 6
+  },
+  "plugins": [
+    "promise"
+  ],
+  "extends": "eslint:recommended",
+  "rules": {
+    // Removed rule "disallow the use of console" from recommended eslint rules
+    "no-console": "off",
+
+    // Removed rule "disallow multiple spaces in regular expressions" from recommended eslint rules
+    "no-regex-spaces": "off",
+
+    // Removed rule "disallow the use of debugger" from recommended eslint rules
+    "no-debugger": "off",
+
+    // Removed rule "disallow unused variables" from recommended eslint rules
+    "no-unused-vars": "off",
+
+    // Removed rule "disallow mixed spaces and tabs for indentation" from recommended eslint rules
+    "no-mixed-spaces-and-tabs": "off",
+
+    // Removed rule "disallow the use of undeclared variables unless mentioned in /*global */ comments" from recommended eslint rules
+    "no-undef": "off",
+
+    // Warn against template literal placeholder syntax in regular strings
+    "no-template-curly-in-string": 1,
+
+    // Warn if return statements do not either always or never specify values
+    "consistent-return": 1,
+
+    // Warn if no return statements in callbacks of array methods
+    "array-callback-return": 1,
+
+    // Requre the use of === and !==
+    "eqeqeq": 2,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    // Disallow the use of alert, confirm, and prompt
+    "no-alert": 2,
+
+    // Disallow the use of arguments.caller or arguments.callee
+    "no-caller": 2,
+
+    // Disallow null comparisons without type-checking operators
+    "no-eq-null": 2,
+
+    // Disallow the use of eval()
+    "no-eval": 2,
+
+    // Warn against extending native types
+    "no-extend-native": 1,
+
+    // Warn against unnecessary calls to .bind()
+    "no-extra-bind": 1,
+
+    // Warn against unnecessary labels    
+    "no-extra-label": 1,
+
+    // Disallow leading or trailing decimal points in numeric literals
+    "no-floating-decimal": 2,
+
+    // Warn against shorthand type conversions
+    "no-implicit-coercion": 1,
+
+    // Warn against function declarations and expressions inside loop statements
+    "no-loop-func": 1,
+
+    // Disallow new operators with the Function object
+    "no-new-func": 2,
+
+    // Warn against new operators with the String, Number, and Boolean objects
+    "no-new-wrappers": 1,
+
+    // Disallow throwing literals as exceptions
+    "no-throw-literal": 2,
+
+    // Require using Error objects as Promise rejection reasons
+    "prefer-promise-reject-errors": 2,
+
+    // Enforce “for” loop update clause moving the counter in the right direction
+    "for-direction": 2,
+
+    // Enforce return statements in getters
+    "getter-return": 2,
+
+    // Disallow await inside of loops
+    "no-await-in-loop": 2,
+
+    // Disallow comparing against -0
+    "no-compare-neg-zero": 2,
+
+    // Warn against catch clause parameters from shadowing variables in the outer scope
+    "no-catch-shadow": 1,
+
+    // Disallow identifiers from shadowing restricted names
+    "no-shadow-restricted-names": 2,
+
+    // Enforce return statements in callbacks of array methods
+    "callback-return": 2,
+
+    // Require error handling in callbacks
+    "handle-callback-err": 2,
+
+    // Warn against string concatenation with __dirname and __filename
+    "no-path-concat": 1,
+
+    // Prefer using arrow functions for callbacks
+    "prefer-arrow-callback": 1,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    //Enforces the use of catch() on un-returned promises
+    "promise/catch-or-return": 2,
+
+    // Warn against nested then() or catch() statements
+    "promise/no-nesting": 1
+  }
+}
diff --git a/username-password-auth/functions/index.js b/username-password-auth/functions/index.js
index 89c4fd3106..31a8840153 100644
--- a/username-password-auth/functions/index.js
+++ b/username-password-auth/functions/index.js
@@ -19,7 +19,7 @@ const functions = require('firebase-functions');
 
 // CORS Express middleware to enable CORS Requests.
 const cors = require('cors')({
-  origin: true
+  origin: true,
 });
 
 // Firebase Setup
@@ -27,7 +27,7 @@ const admin = require('firebase-admin');
 const serviceAccount = require('./service-account.json');
 admin.initializeApp({
   credential: admin.credential.cert(serviceAccount),
-  databaseURL: `https://${process.env.GCLOUD_PROJECT}.firebaseio.com`
+  databaseURL: `https://${process.env.GCLOUD_PROJECT}.firebaseio.com`,
 });
 
 // We use Request to make the basic authentication request in our example.
@@ -45,19 +45,19 @@ const basicAuthRequest = require('request');
 exports.auth = functions.https.onRequest((req, res) => {
   const handleError = (username, error) => {
     console.error({
-      User: username
+      User: username,
     }, error);
     return res.sendStatus(500);
   };
 
   const handleResponse = (username, status, body) => {
     console.log({
-      User: username
+      User: username,
     }, {
       Response: {
         Status: status,
-        Body: body
-      }
+        Body: body,
+      },
     });
     if (body) {
       return res.status(200).json(body);
@@ -82,24 +82,25 @@ exports.auth = functions.https.onRequest((req, res) => {
       }
 
       // TODO(DEVELOPER): In production you'll need to update the `authenticate` function so that it authenticates with your own credentials system.
-      authenticate(username, password).then(valid => {
+      return authenticate(username, password).then((valid) => {
         if (!valid) {
           return handleResponse(username, 401); // Invalid username/password
         }
 
         // On success return the Firebase Custom Auth Token.
-        return admin.auth().createCustomToken(username).then(firebaseToken => {
-          return handleResponse(username, 200, {
-            token: firebaseToken
-          });
+        return admin.auth().createCustomToken(username);
+      }).then((firebaseToken) => {
+        return handleResponse(username, 200, {
+          token: firebaseToken,
         });
-      }).catch(error => {
+      }).catch((error) => {
         return handleError(username, error);
       });
     });
   } catch (error) {
     return handleError(username, error);
   }
+  return null;
 });
 
 /**
@@ -108,15 +109,14 @@ exports.auth = functions.https.onRequest((req, res) => {
  * @returns {Promise<boolean>} success or failure.
  */
 function authenticate(username, password) {
-
   // For the purpose of this example use httpbin (https://httpbin.org) and send a basic authentication request.
   // (Only a password of `Testing123` will succeed)
   const authEndpoint = `https://httpbin.org/basic-auth/${username}/Testing123`;
   const creds = {
     auth: {
       user: username,
-      pass: password
-    }
+      pass: password,
+    },
   };
   return new Promise((resolve, reject) => {
     basicAuthRequest(authEndpoint, creds, (error, response, body) => {