Refactor ESLint config to better support external configs

This should make using `codeclimate prepare` to use external configs simpler:
I've moved all things that might vary by project into an example base file, and
only keep rules in the two other files (base for all projects, and the ES6
variant to additionally pull in for ES6 projects).

Author: wfleming

javascript/README.md

@@ -2,9 +2,12 @@
 
 ## ESLint
 
-This repo contains an `eslintrc.js` file that should be included (as
-`.eslintrc.js`) in each project. Periodically, a repo's `.eslintrc.js` file
-should be synced with the one here.
+This repo contains an `eslintrc.base.js` file specifying rules useful for all
+projects, as well as an `eslintrc.es6.js` with rules specific to ES6 projects.
+
+We suggest creating an `.eslintrc.js` in your own project based on the
+`eslintrc.example.js` file here, using `codeclimate prepare` to pull in the base
+rules (and the ES6 rules if appropriate).
 
 ### Variable and Function Names
 
@@ -46,8 +49,8 @@ api.getModel("id").then(function(data) {
 ### ECMAScript 6
 
 There is an additional set of ESLint rules we use for ES6 code: these are in
-`eslintrc-es6.js`, and can be included into the main `.eslintrc.js` file in ES6
-projects with an `"extends"` directive.
+`eslintrc.es6.js`, and can be included into your `.eslintrc.js` with an
+`"extends"` directive.
 
 The rules there are mostly self explanatory, with one perhaps requiring an
 explanatory note: `=>` functions are preferred over the `var self = this;`

javascript/eslintrc.js renamed to javascript/eslintrc.base.js

@@ -1,10 +1,4 @@
 module.exports = {
-  "env": {
-    "node": true,     // When in a backend context
-    "browser": true,  // When in a web context
-    "jquery": true,   // When in a web context
-    "es6": true,      // When using ES6 features
-  },
   "rules": {
     "brace-style": [2, "1tbs", { "allowSingleLine": true }],
     "camelcase": [2, { "properties": "always" }],
@@ -23,9 +17,4 @@ module.exports = {
     "space-infix-ops": 2,
     "strict": 0,
   },
-  /**
-   *  globals should be defined per file when possible. Use the directive here
-   *  when there are project-level globals (such as jquery)
-   */
-  "globals": {},
 };

javascript/eslintrc-es6.js renamed to javascript/eslintrc.es6.js

@@ -0,0 +1,18 @@
+module.exports = {
+  "env": {
+    "node": true,     // When in a backend context
+    "browser": true,  // When in a web context
+    "jquery": true,   // When in a web context
+    "es6": true,      // When using ES6 features
+  },
+  // It's recommended these files be pulled in via `codeclimate prepare`
+  extends: [
+    ".eslintrc.base.js",
+    ".eslintrc.es6.js" // only for ES6 projects
+  ],
+  /**
+   *  globals should be defined per file when possible. Use the directive here
+   *  when there are project-level globals (such as jquery)
+   */
+  "globals": {},
+};