Strict ESLint config for React, ES6 (based on Airbnb Code style)

.eslintrc.js

{
  "env": {
    "browser": true,
    "node": true,
    "es6": true
  },

  "plugins": ["react"],

  "ecmaFeatures": {
    "arrowFunctions": true,
    "binaryLiterals": true,
    "blockBindings": true,
    "classes": true,
    "defaultParams": true,
    "destructuring": true,
    "forOf": true,
    "generators": true,
    "modules": true,
    "objectLiteralComputedProperties": true,
    "objectLiteralDuplicateProperties": true,
    "objectLiteralShorthandMethods": true,
    "objectLiteralShorthandProperties": true,
    "octalLiterals": true,
    "regexUFlag": true,
    "regexYFlag": true,
    "spread": true,
    "superInFunctions": true,
    "templateStrings": true,
    "unicodeCodePointEscapes": true,
    "globalReturn": true,
    "jsx": true
  },

  "rules": {

    //
    //Possible Errors
    //
    // The following rules point out areas where you might have made mistakes.
    //
    "comma-dangle": 2, // disallow or enforce trailing commas
    "no-cond-assign": 2, // disallow assignment in conditional expressions
    "no-console": 1, // disallow use of console (off by default in the node environment)
    "no-constant-condition": 2, // disallow use of constant expressions in conditions
    "no-control-regex": 2, // disallow control characters in regular expressions
    "no-debugger": 2, // disallow use of debugger
    "no-dupe-args": 2, // disallow duplicate arguments in functions
    "no-dupe-keys": 2, // disallow duplicate keys when creating object literals
    "no-duplicate-case": 2, // disallow a duplicate case label.
    "no-empty": 2, // disallow empty statements
    "no-empty-class": 2, // disallow the use of empty character classes in regular expressions
    "no-ex-assign": 2, // disallow assigning to the exception in a catch block
    "no-extra-boolean-cast": 2, // disallow double-negation boolean casts in a boolean context
    "no-extra-parens": 0, // disallow unnecessary parentheses (off by default)
    "no-extra-semi": 2, // disallow unnecessary semicolons
    "no-func-assign": 2, // disallow overwriting functions written as function declarations
    "no-inner-declarations": 2, // disallow function or variable declarations in nested blocks
    "no-invalid-regexp": 2, // disallow invalid regular expression strings in the RegExp constructor
    "no-irregular-whitespace": 2, // disallow irregular whitespace outside of strings and comments
    "no-negated-in-lhs": 2, // disallow negation of the left operand of an in expression
    "no-obj-calls": 2, // disallow the use of object properties of the global object (Math and JSON) as functions
    "no-regex-spaces": 2, // disallow multiple spaces in a regular expression literal
    "no-reserved-keys": 2, // disallow reserved words being used as object literal keys (off by default)
    "no-sparse-arrays": 2, // disallow sparse arrays
    "no-unreachable": 2, // disallow unreachable statements after a return, throw, continue, or break statement
    "use-isnan": 2, // disallow comparisons with the value NaN
    "valid-jsdoc": 2, // Ensure JSDoc comments are valid (off by default)
    "valid-typeof": 2, // Ensure that the results of typeof are compared against a valid string

    //
    // Best Practices
    //
    // These are rules designed to prevent you from making mistakes.
    // They either prescribe a better way of doing something or help you avoid footguns.
    //
    "block-scoped-var": 0, // treat var statements as if they were block scoped (off by default). 0: deep destructuring is not compatible https://github.com/eslint/eslint/issues/1863
    "complexity": 0, // specify the maximum cyclomatic complexity allowed in a program (off by default)
    "consistent-return": 2, // require return statements to either always or never specify values
    "curly": 2, // specify curly brace conventions for all control statements
    "default-case": 2, // require default case in switch statements (off by default)
    "dot-notation": 2, // encourages use of dot notation whenever possible
    "eqeqeq": 2, // require the use of === and !==
    "guard-for-in": 2, // make sure for-in loops have an if statement (off by default)
    "no-alert": 2, // disallow the use of alert, confirm, and prompt
    "no-caller": 2, // disallow use of arguments.caller or arguments.callee
    "no-div-regex": 2, // disallow division operators explicitly at beginning of regular expression (off by default)
    "no-else-return": 2, // disallow else after a return in an if (off by default)
    "no-empty-label": 2, // disallow use of labels for anything other then loops and switches
    "no-eq-null": 2, // disallow comparisons to null without a type-checking operator (off by default)
    "no-eval": 2, // disallow use of eval()
    "no-extend-native": 2, // disallow adding to native types
    "no-extra-bind": 2, // disallow unnecessary function binding
    "no-fallthrough": 2, // disallow fallthrough of case statements
    "no-floating-decimal": 2, // disallow the use of leading or trailing decimal points in numeric literals (off by default)
    "no-implied-eval": 2, // disallow use of eval()-like methods
    "no-iterator": 2, // disallow usage of __iterator__ property
    "no-labels": 2, // disallow use of labeled statements
    "no-lone-blocks": 2, // disallow unnecessary nested blocks
    "no-loop-func": 2, // disallow creation of functions within loops
    "no-multi-spaces": 2, // disallow use of multiple spaces
    "no-multi-str": 2, // disallow use of multiline strings
    "no-native-reassign": 2, // disallow reassignments of native objects
    "no-new": 2, // disallow use of new operator when not part of the assignment or comparison
    "no-new-func": 2, // disallow use of new operator for Function object
    "no-new-wrappers": 2, // disallows creating new instances of String,Number, and Boolean
    "no-octal": 2, // disallow use of octal literals
    "no-octal-escape": 2, // disallow use of octal escape sequences in string literals, such as var foo = "Copyright \251";
    "no-param-reassign": 2, // disallow reassignment of function parameters (off by default)
    "no-process-env": 2, // disallow use of process.env (off by default)
    "no-proto": 2, // disallow usage of __proto__ property
    "no-redeclare": 2, // disallow declaring the same variable more then once
    "no-return-assign": 2, // disallow use of assignment in return statement
    "no-script-url": 2, // disallow use of javascript: urls.
    "no-self-compare": 2, // disallow comparisons where both sides are exactly the same (off by default)
    "no-sequences": 2, // disallow use of comma operator
    "no-throw-literal": 2, // restrict what can be thrown as an exception (off by default)
    "no-unused-expressions": 2, // disallow usage of expressions in statement position
    "no-void": 2, // disallow use of void operator (off by default)
    "no-warning-comments": [0, {"terms": ["todo", "fixme"], "location": "start"}], // disallow usage of configurable warning terms in comments": 2, // e.g. TODO or FIXME (off by default)
    "no-with": 2, // disallow use of the with statement
    "radix": 2, // require use of the second argument for parseInt() (off by default)
    "vars-on-top": 2, // requires to declare all vars on top of their containing scope (off by default)
    "wrap-iife": 2, // require immediate function invocation to be wrapped in parentheses (off by default)
    "yoda": 2, // require or disallow Yoda conditions

    //
    // Strict Mode
    //
    // These rules relate to using strict mode.
    //
    "strict": 0, // controls location of Use Strict Directives. 0: required by `babel-eslint`

    //
    // Variables
    //
    // These rules have to do with variable declarations.
    //
    "no-catch-shadow": 2, // disallow the catch clause parameter name being the same as a variable in the outer scope (off by default in the node environment)
    "no-delete-var": 2, // disallow deletion of variables
    "no-label-var": 2, // disallow labels that share a name with a variable
    "no-shadow": 2, // disallow declaration of variables already declared in the outer scope
    "no-shadow-restricted-names": 2, // disallow shadowing of names such as arguments
    "no-undef": 2, // disallow use of undeclared variables unless mentioned in a /*global */ block
    "no-undef-init": 2, // disallow use of undefined when initializing variables
    "no-undefined": 2, // disallow use of undefined variable (off by default)
    "no-unused-vars": 2, // disallow declaration of variables that are not used in the code
    "no-use-before-define": 2, // disallow use of variables before they are defined

    //
    //Stylistic Issues
    //
    // These rules are purely matters of style and are quite subjective.
    //
    "indent": [1, 2], // this option sets a specific tab width for your code (off by default)
    "brace-style": 1, // enforce one true brace style (off by default)
    "camelcase": 1, // require camel case names
    "comma-spacing": [1, {"before": false, "after": true}], // enforce spacing before and after comma
    "comma-style": [1, "last"], // enforce one true comma style (off by default)
    "consistent-this": [1, "_this"], // enforces consistent naming when capturing the current execution context (off by default)
    "eol-last": 1, // enforce newline at the end of file, with no multiple empty lines
    "func-names": 0, // require function expressions to have a name (off by default)
    "func-style": 0, // enforces use of function declarations or expressions (off by default)
    "key-spacing": [1, {"beforeColon": false, "afterColon": true}], // enforces spacing between keys and values in object literal properties
    "max-nested-callbacks": [1, 3], // specify the maximum depth callbacks can be nested (off by default)
    "new-cap": [1, {newIsCap: true, capIsNew: false}], // require a capital letter for constructors
    "new-parens": 1, // disallow the omission of parentheses when invoking a constructor with no arguments
    "newline-after-var": 0, // allow/disallow an empty newline after var statement (off by default)
    "no-array-constructor": 1, // disallow use of the Array constructor
    "no-inline-comments": 1, // disallow comments inline after code (off by default)
    "no-lonely-if": 1, // disallow if as the only statement in an else block (off by default)
    "no-mixed-spaces-and-tabs": 1, // disallow mixed spaces and tabs for indentation
    "no-multiple-empty-lines": [1, {"max": 2}], // disallow multiple empty lines (off by default)
    "no-nested-ternary": 1, // disallow nested ternary expressions (off by default)
    "no-new-object": 1, // disallow use of the Object constructor
    "no-spaced-func": 1, // disallow space between function identifier and application
    "no-ternary": 0, // disallow the use of ternary operators (off by default)
    "no-trailing-spaces": 1, // disallow trailing whitespace at the end of lines
    "no-underscore-dangle": 1, // disallow dangling underscores in identifiers
    "no-wrap-func": 1, // disallow wrapping of non-IIFE statements in parens
    "one-var": [1, "never"], // allow just one var statement per function (off by default)
    "operator-assignment": [1, "never"], // require assignment operator shorthand where possible or prohibit it entirely (off by default)
    "padded-blocks": [1, "never"], // enforce padding within blocks (off by default)
    "quote-props": [1, "as-needed"], // require quotes around object literal property names (off by default)
    "quotes": [1, "single"], // specify whether double or single quotes should be used
    "semi": [1, "always"], // require or disallow use of semicolons instead of ASI
    "semi-spacing": [1, {"before": false, "after": true}], // enforce spacing before and after semicolons
    "sort-vars": 0, // sort variables within the same declaration block (off by default)
    "space-after-keywords": [1, "always"], // require a space after certain keywords (off by default)
    "space-before-blocks": [1, "always"], // require or disallow space before blocks (off by default)
    "space-before-function-paren": [1, {"anonymous": "always", "named": "never"}], // require or disallow space before function opening parenthesis (off by default)
    "space-in-brackets": [1, "never"], // require or disallow spaces inside brackets (off by default)
    "space-in-parens": [1, "never"], // require or disallow spaces inside parentheses (off by default)
    "space-infix-ops": [1, "always"], // require spaces around operators
    "space-return-throw-case": [1, "always"], // require a space after return, throw, and case
    "space-unary-ops": [1, {"words": true, "nonwords": false}], // Require or disallow spaces before/after unary operators (words on by default, nonwords off by default)
    "spaced-line-comment": [1, "always"], // require or disallow a space immediately following the // in a line comment (off by default)
    "wrap-regex": 0, // require regex literals to be wrapped in parentheses (off by default)

    //
    // ECMAScript 6
    //
    // These rules are only relevant to ES6 environments and are off by default.
    //
    "no-var": 2, // require let or const instead of var (off by default)
    "generator-star-spacing": [2, "before"], // enforce the spacing around the * in generator functions (off by default)

    //
    // Legacy
    //
    // The following rules are included for compatibility with JSHint and JSLint.
    // While the names of the rules may not match up with the JSHint/JSLint counterpart,
    // the functionality is the same.
    //
    "max-depth": [2, 3], // specify the maximum depth that blocks can be nested (off by default)
    "max-len": [2, 100, 2], // specify the maximum length of a line in your program (off by default)
    "max-params": [2, 5], // limits the number of parameters that can be used in the function declaration. (off by default)
    "max-statements": 0, // specify the maximum number of statement allowed in a function (off by default)
    "no-bitwise": 0, // disallow use of bitwise operators (off by default)
    "no-plusplus": 2, // disallow use of unary operators, ++ and -- (off by default)

    //
    // eslint-plugin-react
    //
    // React specific linting rules for ESLint
    //
    "react/display-name": 0, // Prevent missing displayName in a React component definition
    "react/jsx-quotes": [2, "double", "avoid-escape"], // Enforce quote style for JSX attributes
    "react/jsx-no-undef": 2, // Disallow undeclared variables in JSX
    "react/jsx-sort-props": 0, // Enforce props alphabetical sorting
    "react/jsx-uses-react": 2, // Prevent React to be incorrectly marked as unused
    "react/jsx-uses-vars": 2, // Prevent variables used in JSX to be incorrectly marked as unused
    "react/no-did-mount-set-state": 2, // Prevent usage of setState in componentDidMount
    "react/no-did-update-set-state": 2, // Prevent usage of setState in componentDidUpdate
    "react/no-multi-comp": 0, // Prevent multiple component definition per file
    "react/no-unknown-property": 2, // Prevent usage of unknown DOM property
    "react/prop-types": 2, // Prevent missing props validation in a React component definition
    "react/react-in-jsx-scope": 2, // Prevent missing React when using JSX
    "react/self-closing-comp": 2, // Prevent extra closing tags for components without children
    "react/wrap-multilines": 2, // Prevent missing parentheses around multilines JSX
  }
}

index.html

<html>
<head>
  <title>Build</title>
  <meta http-equiv="Content-type" content="text/html; charset=utf-8" />
</head>
<body>
<div id="app"></div>
</body>
<script src="/assets/bundle.js"></script>
</html>

package.json

{
  "name": "project",
  "version": "1.0.0",
  "description": "Project",
  "engines": {
    "iojs": "1.3.0"
  },
  "scripts": {
    "start": "node --es_staging --harmony_arrow_functions server.js",
    "build": "rm -rf public && cp -pr src/static/ public && webpack",
    "lint": "npm run lint:node && npm run lint:browser",
    "lint:node": "eslint --config=./.eslintrc *.js scripts/*.js",
    "lint:browser": "eslint --config=./src/.eslintrc src/**/**/*.js"
  },
  "dependencies": {
    "babel-core": "^4.7.16",
    "babel-loader": "^4.2.0",
    "css-loader": "^0.9.1",
    "eslint": "^0.18.0",
    "eslint-loader": "^0.9.0",
    "eslint-plugin-react": "^2.0.2",
    "file-loader": "^0.8.1",
    "lodash": "^3.6.0",
    "react": "^0.13.1",
    "react-hot-loader": "^1.2.4",
    "sorted-object": "^1.0.0",
    "style-loader": "^0.9.0",
    "url-loader": "^0.5.5",
    "webpack": "^1.7.3",
    "webpack-dev-server": "^1.7.0"
  }
}

server.js

'use strict';

let path = require('path');
let webpack = require('webpack');
let WebpackDevServer = require('webpack-dev-server');
let config = require('./webpack.config.js').development;

let server = new WebpackDevServer(webpack(config), {
  contentBase: 'src/static/',
  stats: {
    // Do not show list of hundreds of files included in a bundle
    chunkModules: false,
    colors: true
  },
  publicPath: '/assets/',
  hot: true
});

server.use('/', (req, res) => res.sendFile(path.join(__dirname, '/src/static/index.html')));

server.listen(3000, 'localhost', err =>
  err ? console.error(err) : console.log('Listening on http://localhost:3000'));

webpack.config.js

'use strict';


const path = require('path');
const webpack = require('webpack');
const _ = require('lodash');
const embedFileSize = 65536;

const config = {
  entry: [
    './src/index'
  ],
  output: {
    path: path.join(__dirname, 'public', 'assets'),
    filename: 'bundle.js',
    publicPath: '/assets/'
  },
  plugins: [
    new webpack.optimize.DedupePlugin(),
    new webpack.NoErrorsPlugin()
  ],
  resolve: {
    extensions: ['', '.js']
  },
  module: {
    loaders: [
      {test: /\.css$/, loader: 'style!css?sourceMap'},
      {test: /\.json$/, loader: 'json'},
      {test: /\.mp4/, loader: 'url?limit=' + embedFileSize + '&mimetype=video/mp4'},
      {test: /\.svg/, loader: 'url?limit=' + embedFileSize + '&mimetype=image/svg+xml'},
      {test: /\.png$/, loader: 'url?limit=' + embedFileSize + '&mimetype=image/png'},
      {test: /\.jpg/, loader: 'url?limit=' + embedFileSize + '&mimetype=image/jpeg'},
      {test: /\.gif/, loader: 'url?limit=' + embedFileSize + '&mimetype=image/gif'},
      {
        test: /\.(otf|eot|ttf|woff|woff2)(\?v=[0-9]\.[0-9]\.[0-9])?$/,
        loader: 'url?limit=' + embedFileSize
      }
    ],
    preLoaders: [
      {
        test: /\.js$/,
        loaders: ['eslint'],
        include: [new RegExp(path.join(__dirname, 'src'))]
      }
    ]
  },
  node: {
    __filename: true
  },
  stats: {
    colors: true
  },
  eslint: {
    configFile: 'src/.eslintrc'
  }
};

const production = _.extend({}, config, {
  plugins: config.plugins.concat(new webpack.NoErrorsPlugin()),
  module: _.extend({}, config.module, {
    loaders: config.module.loaders.concat({
      test: /\.js$/,
      loaders: ['babel'],
      include: [new RegExp(path.join(__dirname, 'src'))]
    })
  }),
  eslint: _.extend({}, config.eslint, {emitError: true})
});

const development = _.extend({}, config, {
  entry: config.entry.concat([
    'webpack-dev-server/client?http://localhost:3000',
    'webpack/hot/only-dev-server'
  ]),
  plugins: config.plugins.concat(new webpack.HotModuleReplacementPlugin()),
  module: _.extend({}, config.module, {
    loaders: config.module.loaders.concat({
      test: /\.js$/,
      loaders: ['babel', 'react-hot'],
      include: [new RegExp(path.join(__dirname, 'src'))]
    })
  }),
  devtool: 'eval'
});


module.exports = production;
module.exports.development = development;

Note: added .js to .eslintrc configuration file just to have proper code highlighting here in gist.

I use iojs here, so I can use ES6 in server.js and webpack.config.js. If you are still on nodejs, just update code accordingly.

See working minimal example project at https://github.com/nkbt/esnext-quickstart

    Configuration for rule "space-infix-ops" is invalid:
    Value "always" is the wrong type.

eslint v0.23.0

Change it to
"space-infix-ops": [1, {"int32Hint": false}]
http://eslint.org/docs/rules/space-infix-ops.html

Inconsistent formatting

"key-spacing": [1, {"beforeColon": false, "afterColon": true}],

vs

"new-cap": [1, {newIsCap: true, capIsNew: false}],

Also, trailing comma on the last rule

"react/wrap-multilines": 2,

Some error/warning messages I've come across:

Need to be replaced:

• no-empty-class was removed and replaced by: no-empty-character-class
• space-after-keywords was removed and replaced by: keyword-spacing (keyword-spacing)
• space-return-throw-case was removed and replaced by: keyword-spacing
• space-in-brackets was removed and replaced by: object-curly-spacing, array-bracket-spacing, computed-property-spacing
• spaced-line-comment was removed and replaced by: spaced-comment

Need to be removed (their replacements are already in the file):

• no-empty-label was removed and replaced by: no-labels
• no-reserved-keys was removed and replaced by: quote-props