.eslintrc.js

const OFF = 0
const WARN = 1
const ON = 2
const YES = true

const noUselessRenameOpts = {
  ignoreDestructuring: false,
  ignoreImport: false,
  ignoreExport: false,
}

module.exports = {
  root: YES,
  reportUnusedDisableDirectives: YES,

  parserOptions: {
    impliedStrict: YES,
    sourceType: 'module',
  },

  // https://github.com/sindresorhus/globals/blob/master/globals.json
  env: {
    node: YES,
    es2017: YES,
  },

  // https://github.com/eslint/eslint/blob/master/conf/eslint-recommended.js
  extends: ['eslint:recommended'],

  rules: {
    'accessor-pairs': ON,
    'array-callback-return': ON,
    'block-scoped-var': ON,
    'complexity': [ON, 8], // default is 20
    'consistent-return': ON,
    'consistent-this': [ON, '_self'],
    'dot-notation': WARN,
    'eol-last': ON,
    'eqeqeq': [ON, 'always', { null: 'ignore' }],
    'for-direction': ON,
    'func-call-spacing': ON,
    'getter-return': ON,
    'guard-for-in': WARN,
    'handle-callback-err': [ON, '^err(or)?$'],
    'keyword-spacing': ON,
    'linebreak-style': [ON, 'unix'],
    'max-depth': [ON, 3],
    'max-len': [1, 120, 4, { ignoreUrls: YES, ignoreRegExpLiterals: YES }],
    'max-lines-per-function': [ON, { max: 25, skipBlankLines: YES, skipComments: YES }],
    'max-lines': OFF,
    'max-nested-callbacks': [ON, 3], // default is 10
    'max-params': [ON, 3],
    'max-statements': [ON, 12],
    'new-cap': [ON, { newIsCap: true, capIsNew: false }],
    'new-parens': ON,
    'no-alert': ON,
    'no-array-constructor': ON,
    'no-caller': ON,
    'no-catch-shadow': ON,
    'no-console': ON,
    'no-div-regex': ON,
    'no-dupe-args': ON,
    'no-dupe-class-members': ON,
    'no-dupe-else-if': ON,
    'no-dupe-keys': ON,
    'no-duplicate-imports': [ON, { includeExports: YES }],
    'no-else-return': ON,
    'no-empty-pattern': ON,
    'no-eval': ON,
    'no-ex-assign': ON,
    'no-extend-native': ON,
    'no-extra-bind': ON,
    'no-extra-boolean-cast': ON,
    'no-extra-label': ON,
    'no-fallthrough': ON,
    'no-func-assign': ON,
    'no-global-assign': ON,
    'no-implicit-globals': ON,
    'no-implied-eval': ON,
    'no-import-assign': ON,
    'no-inner-declarations': [ON, 'functions'],
    'no-invalid-regexp': ON,
    'no-irregular-whitespace': ON,
    'no-iterator': ON,
    'no-label-var': ON,
    'no-labels': [ON, { allowLoop: false, allowSwitch: false }],
    'no-lone-blocks': ON,
    'no-lonely-if': ON,
    'no-loop-func': ON,
    'no-loss-of-precision': WARN,
    'no-misleading-character-class': ON,
    'no-multi-str': ON,
    'no-multiple-empty-lines': [ON, { max: 2 }],
    'no-native-reassign': ON,
    'no-new-func': ON,
    'no-new-object': ON,
    'no-new-symbol': ON,
    'no-new-wrappers': ON,
    'no-new': ON,
    'no-obj-calls': WARN,
    'no-octal-escape': ON,
    'no-octal': ON,
    'no-proto': ON,
    'no-prototype-builtins': WARN,
    'no-redeclare': ON,
    'no-regex-spaces': ON,
    'no-return-assign': [ON, 'except-parens'],
    'no-return-await': ON,
    'no-script-url': ON,
    'no-self-assign': ON,
    'no-self-compare': ON,
    'no-sequences': ON,
    'no-shadow-restricted-names': ON,
    'no-sparse-arrays': ON,
    'no-template-curly-in-string': ON,
    'no-this-before-super': ON,
    'no-throw-literal': ON,
    'no-undef-init': ON,
    'no-undef': ON,
    'no-unmodified-loop-condition': WARN,
    'no-unneeded-ternary': [ON, { defaultAssignment: false }],
    'no-unreachable': ON,
    'no-unsafe-finally': ON,
    'no-unsafe-negation': ON,
    'no-unused-labels': ON,
    'no-useless-backreference': ON,
    'no-unused-expressions': WARN,
    'no-unused-vars': ON,
    'no-use-before-define': [ON, { functions: false }],
    'no-useless-call': ON,
    'no-useless-computed-key': ON,
    'no-useless-concat': ON,
    'no-useless-escape': ON,
    'no-useless-rename': [ON, noUselessRenameOpts],
    'no-useless-return': ON,
    'no-var': ON,
    'no-void': ON,
    'no-whitespace-before-property': ON,
    'no-with': ON,
    'object-curly-spacing': [ON, 'always'],
    'one-var-declaration-per-line': ON,
    'one-var': [ON, { initialized: 'never' }],
    'prefer-const': [ON, { destructuring: 'all' }],
    'prefer-numeric-literals': ON,
    'prefer-promise-reject-errors': ON,
    'radix': ON,
    'require-atomic-updates': ON,
    'require-await': ON,
    'require-yield': ON,
    'strict': [ON, 'never'],
    'symbol-description': ON,
    'unicode-bom': [ON, 'never'],
    'use-isnan': ON,
    'valid-typeof': [ON, { requireStringLiterals: true }],
    'yoda': [ON, 'never'],
  },
  overrides: [
    {
      files: ['**/test/**'],
      env: {
        mocha: YES,
      },
      rules: {
        'no-console': OFF,
        'max-len': OFF,
        'max-lines-per-function': OFF,
      },
    },
  ],
}