ESLint config

.eslintrc.js

/* eslint-disable max-lines, no-magic-numbers */
/* eslint-env node */
module.exports = {
    root: true,
	// Uses the typescript parser for ease of use and "new features".
	// (a.k.a.: supported but not in the current js version yet)
    parser: '@typescript-eslint/parser',
    parserOptions: {
        sourceType: 'module',
        ecmaVersion: 12,
        lib: ['ESNext', 'DOM']
    },
    ignorePatterns: ['/build/**', '/dist/**', '/vendor/**'],
    env: {
        browser: true,
        webextensions: true,
        'shared-node-browser': true,
        es6: true,
        es2017: true,
        es2020: true
    },
    plugins: ['jsdoc'],
    rules: {
        // Possible errors
        'for-direction': 'error',
        'getter-return': ['error', { allowImplicit: true }],
        'no-await-in-loop': 'error',
        'no-async-promise-executor': 'error',
        'no-compare-neg-zero': 'error',
        'no-cond-assign': ['error', 'always'],
        'no-console': 'warn',
        'no-constant-condition': 'error',
        'no-control-regex': 'error',
        'no-debugger': 'warn',
        'no-dupe-args': 'error',
        'no-dupe-else-if': 'error',
        'no-dupe-keys': 'error',
        'no-duplicate-case': 'error',
        'no-empty': 'warn',
        'no-empty-character-class': 'error',
        'no-ex-assign': 'error',
        'no-extra-boolean-cast': 'error',
        'no-extra-parens': ['error', 'all', { nestedBinaryExpressions: true }],

        'no-extra-semi': 'error',
        'no-func-assign': 'error',
        'no-import-assign': 'error',
        'no-inner-declarations': ['error', 'both'],
        'no-invalid-regexp': 'error',
        'no-irregular-whitespace': ['error', { skipStrings: true, skipTemplates: true }],
        'no-loss-of-precision': 'error',
        'no-misleading-character-class': 'error',
        'no-obj-calls': 'error',
        'no-promise-executor-return': 'error',
        'no-prototype-builtins': 'warn',
        'no-regex-spaces': 'error',
        'no-setter-return': 'error',
        'no-sparse-arrays': 'error',
        'no-template-curly-in-string': 'warn',
        'no-unexpected-multiline': 'error',
        'no-unreachable': 'error',
        'no-unreachable-loop': 'error',
        'no-unsafe-finally': 'error',
        'no-unsafe-negation': 'error',
        'no-unsafe-optional-chaining': 'error',
        'no-useless-backreference': 'error',
        'require-atomic-updates': 'warn',
        'use-isnan': 'error',
        'valid-typeof': 'warn',

        // Best practices
        'accessor-pairs': 'error',
        'array-callback-return': 'error',
        'block-scoped-var': 'warn',
        'class-methods-use-this': 'warn',
        complexity: 'error',
        'consistent-return': 'warn',
        curly: 'error',
        'default-case': 'warn',
        'default-case-last': 'error',
        'default-param-last': 'error',
        'dot-location': ['warn', 'property'],
        'dot-notation': ['error', { allowPattern: '^[a-z]+(_[a-z]+)+$' }],
        eqeqeq: ['error', 'smart'],
        'grouped-accessor-pairs': 'error',
        'guard-for-in': 'warn',
        'max-classes-per-file': ['warn', 1],
        'no-alert': 'error',
        'no-caller': 'error',
        'no-case-declarations': 'error',
        'no-constructor-return': 'error',
        'no-div-regex': 'error',
        'no-else-return': 'warn',
        'no-empty-function': 'error',
        'no-empty-pattern': 'error',
        'no-eq-null': 'error',
        'no-eval': 'error',
        'no-extend-native': 'error',
        'no-extra-bind': 'error',
        'no-extra-label': 'error',
        'no-fallthrough': 'error',
        'no-floating-decimal': 'error',
        'no-global-assign': 'error',
        'no-implicit-coercion': 'error',
        'no-implicit-globals': 'warn',
        'no-implied-eval': 'error',
        'no-invalid-this': 'warn',
        'no-iterator': 'error',
        'no-labels': 'error',
        'no-lone-blocks': 'error',
        'no-loop-func': 'error',
        'no-magic-numbers': ['warn', { enforceConst: true, ignoreArrayIndexes: true, ignore: [-1, 0, 1, 16] }],
        'no-multi-spaces': 'error',
        'no-multi-str': 'error',
        'no-new': 'error',
        'no-new-func': 'error',
        'no-new-wrappers': 'error',
        'no-nonoctal-decimal-escape': 'error',
        'no-octal': 'error',
        'no-octal-escape': 'error',
        'no-param-reassign': 'warn',
        'no-proto': 'error',
        'no-redeclare': ['error', { builtinGlobals: true }],
        'no-restricted-properties': 'off',
        'no-return-assign': 'error',
        'no-return-await': 'warn',
        'no-script-url': 'error',
        'no-self-assign': ['error', { props: true }],
        'no-self-compare': 'error',
        'no-sequences': 'error',
        'no-throw-literal': 'error',
        'no-unmodified-loop-condition': 'error',
        'no-unused-expressions': ['error', { allowShortCircuit: true, allowTernary: true }],
        'no-unused-labels': 'error',
        'no-useless-call': 'error',
        'no-useless-catch': 'error',
        'no-useless-concat': 'error',
        'no-useless-escape': 'error',
        'no-useless-return': 'error',
        'no-void': 'error',
        'no-warning-comments': 'warn',
        'no-with': 'error',
        'prefer-named-capture-group': 'warn',
        'prefer-promise-reject-errors': 'warn',
        'prefer-regex-literals': 'warn',
        radix: ['error', 'as-needed'],
        'require-await': 'warn',
        'require-unicode-regexp': 'warn',
        'vars-on-top': 'warn',
        'wrap-iife': ['error', 'inside'],
        yoda: 'error',

        // Strict mode
        strict: ['warn', 'function'],

        // Variables
        'init-declarations': 'warn',
        'no-delete-var': 'error',
        'no-label-var': 'error',
        'no-restricted-globals': ['error', 'event'],
        'no-shadow': ['warn', { builtinGlobals: true, hoist: 'all', allow: ['name', 'status', 'self', 'event'] }],
        'no-shadow-restricted-names': 'error',
        'no-undef': ['error', { 'typeof': true }],
        'no-undef-init': 'warn',
        'no-undefined': 'error',
        'no-unused-vars': ['warn', { args: 'all', caughtErrors: 'none', argsIgnorePattern: '^_' }],
        'no-use-before-define': 'error',

        // Stylistic rules
        'array-bracket-newline': 'warn',
        'array-bracket-spacing': 'warn',
        'array-element-newline': ['error', 'consistent'],
        'block-spacing': 'warn',
        'brace-style': ['warn', '1tbs', { allowSingleLine: true }],
        camelcase: 'warn',
        'capitalized-comments': 'warn',
        'comma-dangle': 'warn',
        'comma-spacing': 'warn',
        'comma-style': 'warn',
        'computed-property-spacing': 'warn',
        'consistent-this': ['warn', 'self'],
        'eol-last': ['warn', 'always'],
        'func-call-spacing': 'warn',
        'func-name-matching': 'error',
        'func-names': ['warn', 'as-needed'],
        'func-style': ['warn', 'declaration', { allowArrowFunctions: true }],
        'function-call-argument-newline': ['warn', 'consistent'],
        'function-paren-newline': ['warn', 'consistent'],
        'id-denylist': 'off',
        'id-length': [
            'warn',
            { min: 3, max: 50, properties: 'never', exceptions: ['i', 'j', 'n', 'w', 'x', 'y', 'z', 'cb', 'id', 'fs', 'to', 'up'] }
        ],
        'id-match': 'off',
        'implicit-arrow-linebreak': 'error',
        indent: ['error', 4, { SwitchCase: 1 }],
        'jsx-quotes': 'warn',
        'key-spacing': 'error',
        'keyword-spacing': ['error', { before: true, after: true, overrides: { 'function': { after: false } } }],
        'lines-between-class-members': 'off',
        'line-comment-position': ['error', { position: 'above' }],
        'linebreak-style': 'error',
        'lines-around-comment': 'warn',
        'max-depth': 'warn',
        'max-len': [
            'warn',
            {
                code: 180,
                tabWidth: 4,
                ignoreComments: true,
                ignoreUrls: true,
                ignoreStrings: true,
                ignoreTemplateLiterals: true,
                ignoreRegExpLiterals: true
            }
        ],
        'max-lines': ['warn', 1024],
        'max-lines-per-function': ['warn', { max: 512 }],
        'max-nested-callbacks': 'warn',
        'max-params': ['warn', 6],
        'max-statements': ['warn', 512],
        'max-statements-per-line': 'warn',
        'multiline-comment-style': 'off',
        'multiline-ternary': ['warn', 'always-multiline'],
        'new-cap': 'error',
        'new-parens': 'error',
        'newline-per-chained-call': ['warn', { ignoreChainWithDepth: 6 }],
        'no-array-constructor': 'error',
        'no-bitwise': 'error',
        'no-continue': 'error',
        'no-inline-comments': 'warn',
        'no-lonely-if': 'warn',
        'no-mixed-operators': ['warn', { allowSamePrecedence: true }],
        'no-mixed-spaces-and-tabs': ['error', 'smart-tabs'],
        'no-multi-assign': 'error',
        'no-multiple-empty-lines': ['warn', { max: 2, maxEOF: 0, maxBOF: 0 }],
        'no-negated-condition': 'off',
        'no-nested-ternary': 'error',
        'no-new-object': 'error',
        'no-plusplus': ['warn', { allowForLoopAfterthoughts: true }],
        'no-restricted-syntax': 'off',
        'no-tabs': ['warn', { allowIndentationTabs: true }],
        'no-ternary': 'error',
        'no-trailing-spaces': 'error',
        'no-underscore-dangle': 'error',
        'no-unneeded-ternary': 'error',
        'no-whitespace-before-property': 'warn',
        'nonblock-statement-body-position': 'warn',
        'object-curly-newline': 'warn',
        'object-curly-spacing': ['warn', 'always'],
        'object-property-newline': ['warn', { allowMultiplePropertiesPerLine: true }],
        'one-var': ['warn', 'never'],
        'one-var-declaration-per-line': 'warn',
        'operator-assignment': 'warn',
        'operator-linebreak': ['error', 'none'],
        'padded-blocks': ['warn', 'never'],
        'padding-line-between-statements': [
            'warn',
            { blankLine: 'always', prev: '*', next: 'return' },
            { blankLine: 'always', prev: ['const', 'let', 'var'], next: '*' },
            { blankLine: 'any', prev: ['const', 'let', 'var'], next: ['const', 'let', 'var'] },
            { blankLine: 'always', prev: 'directive', next: '*' },
            { blankLine: 'any', prev: 'directive', next: 'directive' },
            { blankLine: 'always', prev: 'break', next: ['case', 'default'] }
        ],
        'prefer-exponentiation-operator': 'warn',
        'prefer-object-spread': 'error',
        'quote-props': ['warn', 'as-needed', { keywords: true, numbers: true }],
        quotes: ['warn', 'single', { avoidEscape: true }],
        semi: 'error',
        'semi-spacing': ['warn', { before: false, after: true }],
        'semi-style': 'warn',
        'sort-keys': 'off',
        'sort-vars': 'warn',
        'space-before-blocks': ['warn', { functions: 'always', keywords: 'always' }],
        'space-before-function-paren': ['warn', { anonymous: 'never', named: 'never' }],
        'space-in-parens': 'warn',
        'space-infix-ops': 'warn',
        'space-unary-ops': ['warn', { words: true, nonwords: false }],
        'spaced-comment': 'warn',
        'switch-colon-spacing': 'warn',
        'template-tag-spacing': 'error',
        'unicode-bom': 'error',
        'wrap-regex': 'error',

        // ES6
        'arrow-body-style': 'error',
        'arrow-parens': 'error',
        'arrow-spacing': 'error',
        'constructor-super': 'error',
        'generator-star-spacing': 'error',
        'no-class-assign': 'error',
        'no-confusing-arrow': ['warn', { allowParens: true }],
        'no-const-assign': 'error',
        'no-dupe-class-members': 'error',
        'no-duplicate-imports': 'error',
        'no-new-symbol': 'error',
        'no-restricted-exports': 'off',
        'no-restricted-imports': ['error', 'domain', 'v8', 'vm'],
        'no-this-before-super': 'error',
        'no-useless-computed-key': 'error',
        'no-useless-constructor': 'error',
        'no-useless-rename': 'error',
        'no-var': 'warn',
        'object-shorthand': 'warn',
        'prefer-arrow-callback': 'warn',
        'prefer-const': 'warn',
        'prefer-destructuring': 'warn',
        'prefer-numeric-literals': 'warn',
        'prefer-rest-params': 'warn',
        'prefer-spread': 'warn',
        'prefer-template': 'warn',
        'require-yield': 'error',
        'rest-spread-spacing': 'error',
        'sort-imports': ['warn', { ignoreCase: true, ignoreDeclarationSort: true }],
        'symbol-description': 'error',
        'template-curly-spacing': 'error',
        'yield-star-spacing': 'error',

        // Plugin JSDoc
        'jsdoc/check-access': 'error',
        'jsdoc/check-alignment': 'warn',
        'jsdoc/check-examples': 'warn',
        'jsdoc/check-indentation': 'warn',
        'jsdoc/check-param-names': 'error',
        'jsdoc/check-property-names': 'error',
        'jsdoc/check-syntax': 'warn',
        'jsdoc/check-tag-names': 'error',
        'jsdoc/check-types': 'error',
        'jsdoc/check-values': 'error',
        'jsdoc/empty-tags': 'error',
        'jsdoc/implements-on-classes': 'error',
        'jsdoc/match-description': 'off',
        'jsdoc/newline-after-description': 'error',
        'jsdoc/no-bad-blocks': 'warn',
        'jsdoc/no-defaults': 'off',
        'jsdoc/no-types': 'off',
        'jsdoc/no-undefined-types': 'warn',
        'jsdoc/require-description-complete-sentence': 'warn',
        'jsdoc/require-description': 'warn',
        'jsdoc/require-example': 'off',
        'jsdoc/require-file-overview': 'off',
        'jsdoc/require-hyphen-before-param-description': ['warn', 'never'],
        'jsdoc/require-jsdoc': 'warn',
        'jsdoc/require-param-description': 'error',
        'jsdoc/require-param-name': 'error',
        'jsdoc/require-param-type': 'error',
        'jsdoc/require-param': 'error',
        'jsdoc/require-property-description': 'error',
        'jsdoc/require-property-name': 'error',
        'jsdoc/require-property-type': 'error',
        'jsdoc/require-returns-check': 'error',
        'jsdoc/require-returns-description': 'error',
        'jsdoc/require-returns-type': 'error',
        'jsdoc/require-returns': 'error',
        'jsdoc/require-throws': 'error',
        'jsdoc/valid-types': 'error'
    }
};

This ESLint config has all rules defined, but some are turned off.

It also uses the typescript parser for ease of use in some cases and ease of configure (the babel parser is just harder to configure).