.eslintrc.js

module.exports = {
  // Build upon Airbnb JavaScript style guide
  // https://github.com/airbnb/javascript
  // https://github.com/airbnb/javascript/tree/master/packages/eslint-config-airbnb
  extends: 'airbnb',

  // Environments define global variables that are predefined.
  // http://eslint.org/docs/user-guide/configuring.html#specifying-environments
  env: {
    // Enforce explicit globals via window.foo
    browser: false,
    // jasmine, describe, it, expect etc.
    jasmine: true,
  },

  globals: {
    window: false,
  },

  // Override some rules in the Airbnb style guide to match
  // our setup and preferences.
  rules: {
    // Allow ++ operator
    // https://eslint.org/docs/rules/no-plusplus
    'no-plusplus': 'off',

    // React / JSX
    // -----------
    //
    // The following rules overwrite the AirBnB rules for React / JSX:
    // https://github.com/airbnb/javascript/blob/master/packages/eslint-config-airbnb/rules/react.js

    // In JSX, prefer single quotes
    // https://eslint.org/docs/rules/jsx-quotes
    'jsx-quotes': ['warn', 'prefer-single'],

    // Restrict file extensions that may contain JSX
    // Disable rule since we’re using .js instead of .jsx
    // https://github.com/yannickcr/eslint-plugin-react/blob/master/docs/rules/jsx-filename-extension.md
    'react/jsx-filename-extension': 'off',

    // Prevent missing React when using JSX
    // Disable since it does not make sense for Preact
    // https://github.com/yannickcr/eslint-plugin-react/blob/master/docs/rules/react-in-jsx-scope.md
    'react/react-in-jsx-scope': 'off',

    // Stylistic rules
    // ---------------

    // Limit Maximum Length of Line
    // http://eslint.org/docs/rules/max-len.html
    'max-len': ['warn', 80, 2, { ignoreUrls: true }],

    // eslint-plugin-import
    // --------------------
    //
    // ESLint plugin with rules that help validate proper imports.

    // Ensure imports point to a file/module that can be resolved.
    // Disable since it makes no sense in a Webpack project
    // https://github.com/benmosher/eslint-plugin-import/blob/master/docs/rules/no-unresolved.md
    'import/no-unresolved': 'off',
  },
};