.eslintrc.json

{
  "env": {
    // Defines globals exposed by modern browsers
    "browser": true,
    // Defines globals exposed by jQuery
    "jquery": true,
    // Defines globals exposed by Node.js
    "node": true
  },
  "globals": {
    // Stop complaining that lodash is undefined
    "_": true
  },
  "installedESLint": true,
  "parserOptions": {
    "ecmaFeatures": {
      "experimentalObjectRestSpread": true,
      // add support for JSX
      "jsx": true
    }
  },
  "plugins": [
    "react"
  ],
  // Our rules
  "rules": {

    // Two space indent
    "indent": ["error", 2],

    // Force use of === and !==
    "eqeqeq": ["error"],

    // Spaces and style 
    "array-bracket-spacing": ["error", "never"],
    "block-spacing": ["error", "never"],
    "brace-style": ["error", "1tbs"],
    "camelcase": ["error"],
    "comma-dangle": ["error", "never"],
    "eol-last": "error",

    // Require curly brackets around everything
    // no more if(foo) bar;
    "curly": ["error", "all"],

    // No assignment in conditionals
    // eg. if(foo = "bar"){...}
    // foo is now "bar", regardless
    "no-cond-assign": ["error", "always"],

    // Force double quotes
    // May change to single quotes to match rails
    // styleguide 
    "quotes": ["error","double"],

    // Rquire semicolons
    "semi": ["error","always"],

    // But not too many semicolons
    "no-extra-semi": ["error"],

    // Disable duplicate keys in objects
    // eg. { foo: "bar", foo: "baz" }
    "no-dupe-keys": ["error"],

    // Highlight left over debuggers
    "no-debugger": ["error"],

    // Highlight duplicate case stemement labels
    "no-duplicate-case": ["error"],

    // Require a "default" case in switch statements
    "default-case": ["error"],

    // Stop if(condition) {} else { if(condition} {} }
    // Should be if(condition) {} else if(condition) {}
    "no-lonely-if": "error",

    // Misc best practices 
    "linebreak-style": ["error","unix"],
    "use-isnan": ["error"],
    "no-invalid-regexp": ["error"],
    "strict": ["error", "global"],
    "no-redeclare": ["error", { "builtinGlobals": true }],
    "no-fallthrough": ["error"],
    "no-undef": ["error"],
    "no-unused-vars": ["error"]
  }
}