Prefer arrow functions, const

.eslintrc.json

@@ -13,6 +13,7 @@
         "arrow-spacing": ["error"],
         "no-const-assign": ["error"],
         "prefer-const": ["error"],
+        "prefer-arrow-callback": ["error"],
         "spaced-comment": ["error", "always"],
         "semi": ["error", "always"]
     }

auth/cordova.js

@@ -14,7 +14,7 @@ function createGoogleProvider() {
 
 function cordovaSignInRedirect(provider) {
   // [START auth_cordova_sign_in_redirect]
-  firebase.auth().signInWithRedirect(provider).then(function() {
+  firebase.auth().signInWithRedirect(provider).then(() => {
     return firebase.auth().getRedirectResult();
   }).then((result) => {
     /** @type {firebase.auth.OAuthCredential} */

auth/firebaseui.js

@@ -218,13 +218,13 @@ function fuiConfig() {
   // [START auth_fui_config]
   var uiConfig = {
     callbacks: {
-      signInSuccessWithAuthResult: function(authResult, redirectUrl) {
+      signInSuccessWithAuthResult: (authResult, redirectUrl) => {
         // User successfully signed in.
         // Return type determines whether we continue the redirect automatically
         // or whether we leave that to developer to handle.
         return true;
       },
-      uiShown: function() {
+      uiShown: () => {
         // The widget is rendered.
         // Hide the loader.
         document.getElementById('loader').style.display = 'none';

auth/link-multiple-accounts.js

@@ -41,10 +41,10 @@ function getProviders() {
 function simpleLink(credential) {
   // [START auth_simple_link]
   auth.currentUser.linkWithCredential(credential)
-    .then(function(usercred) {
+    .then((usercred) => {
       var user = usercred.user;
       console.log("Account linking success", user);
-    }).catch(function(error) {
+    }).catch((error) => {
       console.log("Account linking error", error);
     });
   // [END auth_simple_link]
@@ -53,10 +53,10 @@ function simpleLink(credential) {
 function anonymousLink(credential) {
   // [START auth_anonymous_link]
   auth.currentUser.linkWithCredential(credential)
-    .then(function(usercred) {
+    .then((usercred) => {
       var user = usercred.user;
       console.log("Anonymous account successfully upgraded", user);
-    }).catch(function(error) {
+    }).catch((error) => {
       console.log("Error upgrading anonymous account", error);
     });
   // [END auth_anonymous_link]
@@ -66,12 +66,12 @@ function linkWithPopup() {
   var provider = new firebase.auth.GoogleAuthProvider();
 
   // [START auth_link_with_popup]
-  auth.currentUser.linkWithPopup(provider).then(function(result) {
+  auth.currentUser.linkWithPopup(provider).then((result) => {
     // Accounts successfully linked.
     var credential = result.credential;
     var user = result.user;
     // ...
-  }).catch(function(error) {
+  }).catch((error) => {
     // Handle Errors here.
     // ...
   });
@@ -88,14 +88,14 @@ function linkWithRedirect() {
   // [END auth_link_with_redirect]
 
   // [START auth_get_redirect_result]
-  auth.getRedirectResult().then(function(result) {
+  auth.getRedirectResult().then((result) => {
     if (result.credential) {
       // Accounts successfully linked.
       var credential = result.credential;
       var user = result.user;
       // ...
     }
-  }).catch(function(error) {
+  }).catch((error) => {
     // Handle Errors here.
     // ...
   });
@@ -118,7 +118,7 @@ function mergeAccounts(newCredential) {
   repo.delete(prevUser);
 
   // Sign in user with the account you want to link to
-  auth.signInWithCredential(newCredential).then(function(result) {
+  auth.signInWithCredential(newCredential).then((result) => {
     console.log("Sign In Success", result);
     var currentUser = result.user;
     var currentUserData = repo.get(currentUser);
@@ -128,15 +128,15 @@ function mergeAccounts(newCredential) {
     var mergedData = repo.merge(prevUserData, currentUserData);
 
     return prevUser.linkWithCredential(result.credential)
-      .then(function(linkResult) {
+      .then((linkResult) => {
         // Sign in with the newly linked credential
         return auth.signInWithCredential(linkResult.credential);
       })
-      .then(function(signInResult) {
+      .then((signInResult) => {
         // Save the merged data to the new user
         repo.set(signInResult.user, mergedData);
       });
-  }).catch(function(error) {
+  }).catch((error) => {
     // If there are errors we want to undo the data merge/deletion
     console.log("Sign In Error", error);
     repo.set(prevUser, prevUserData);
@@ -157,10 +157,10 @@ function unlink(providerId) {
   var user = auth.currentUser;
 
   // [START auth_unlink_provider]
-  user.unlink(providerId).then(function() {
+  user.unlink(providerId).then(() => {
     // Auth provider unlinked from account
     // ...
-  }).catch(function(error) {
+  }).catch((error) => {
     // An error happened
     // ...
   });

database/read-and-write.js

@@ -20,7 +20,7 @@ function writeUserDataWithCompletion(userId, name, email, imageUrl) {
     username: name,
     email: email,
     profile_picture : imageUrl
-  }, function(error) {
+  }, (error) => {
     if (error) {
       // The write failed...
     } else {

firestore-next/test.firestore.js

@@ -16,15 +16,15 @@ class City {
 }
 
 // Firestore data converter
-var cityConverter = {
-    toFirestore: function(city) {
+const cityConverter = {
+    toFirestore: (city) => {
         return {
             name: city.name,
             state: city.state,
             country: city.country
             };
     },
-    fromFirestore: function(snapshot, options){
+    fromFirestore: (snapshot, options) => {
         const data = snapshot.data(options);
         return new City(data.name, data.state, data.country);
     }
@@ -190,7 +190,7 @@ describe("firestore", () => {
             const q = query(collection(db, "users"), where("born", "<", 1900));
             const unsubscribe = onSnapshot(q, (snapshot) => {
                 console.log("Current users born before 1900:");
-                snapshot.forEach(function (userSnapshot) {
+                snapshot.forEach((userSnapshot) => {
                     console.log(userSnapshot.data());
                 });
             });
@@ -360,7 +360,7 @@ describe("firestore", () => {
             function deleteCollection(db, collectionRef, batchSize) {
               const q = query(collectionRef, orderBy('__name__'), limit(batchSize));
 
-              return new Promise(function(resolve) {
+              return new Promise((resolve) => {
                   deleteQueryBatch(db, q, batchSize, resolve);
               });
             }
@@ -616,7 +616,7 @@ describe("firestore", () => {
             });
             // [END listen_document]
 
-            setTimeout(function() {
+            setTimeout(() => {
                 unsub();
                 done();
             }, 3000);
@@ -632,7 +632,7 @@ describe("firestore", () => {
             });
             // [END listen_document_local]
 
-            setTimeout(function() {
+            setTimeout(() => {
                 unsub();
                 done();
             }, 3000);
@@ -650,7 +650,7 @@ describe("firestore", () => {
               });
             // [END listen_with_metadata]
 
-            setTimeout(function() {
+            setTimeout(() => {
                 unsub();
                 done();
             }, 3000);
@@ -695,7 +695,7 @@ describe("firestore", () => {
               console.log("Current cities in CA: ", cities.join(", "));
             });
             // [END listen_multiple]
-            setTimeout(function() {
+            setTimeout(() => {
                 unsubscribe();
                 done();
             }, 2500);
@@ -720,7 +720,7 @@ describe("firestore", () => {
               });
             });
             // [END listen_diffs]
-            setTimeout(function() {
+            setTimeout(() => {
                 unsubscribe();
                 done();
             }, 2500);