.eslintrc.json

{
  "root": true,
  "env": {
    "node": true,
    "es6": true
  },
  "parserOptions": {
    "ecmaVersion": 2019
  },
  "plugins": [
    "jsdom-internal"
  ],
  "rules": {
    // Possible errors
    "for-direction": "error",
    "getter-return": "error",
    "no-await-in-loop": "error",
    "no-compare-neg-zero": "error",
    "no-cond-assign": ["error", "except-parens"],
    "no-console": "error",
    "no-constant-condition": ["error", { "checkLoops": false }],
    "no-control-regex": "off",
    "no-debugger": "error",
    "no-dupe-args": "error",
    "no-dupe-keys": "error",
    "no-duplicate-case": "error",
    "no-empty": "error",
    "no-empty-character-class": "error",
    "no-ex-assign": "error",
    "no-extra-boolean-cast": "error",
    "no-extra-parens": [
      "error",
      "all",
      { "conditionalAssign": false, "nestedBinaryExpressions": false, "returnAssign": false, "enforceForNewInMemberExpressions": false }
    ],
    "no-extra-semi": "error",
    "no-func-assign": "error",
    "no-inner-declarations": "off",
    "no-invalid-regexp": "error",
    "no-irregular-whitespace": "error",
    "no-obj-calls": "error",
    "no-prototype-builtins": "error",
    "no-regex-spaces": "error",
    "no-sparse-arrays": "error",
    "no-template-curly-in-string": "error",
    "no-unexpected-multiline": "error",
    "no-unreachable": "error",
    "no-unsafe-finally": "off",
    "no-unsafe-negation": "error",
    "use-isnan": "error",
    "valid-jsdoc": "off",
    "valid-typeof": "error",

    // Best practices
    "accessor-pairs": "error",
    "array-callback-return": "error",
    "block-scoped-var": "off",
    "class-methods-use-this": "off",
    "complexity": "off",
    "consistent-return": "error",
    "curly": ["error", "all"],
    "default-case": "off",
    "dot-location": ["error", "property"],
    "dot-notation": "error",
    "eqeqeq": "error",
    "guard-for-in": "off",
    "no-alert": "error",
    "no-caller": "error",
    "no-case-declarations": "error",
    "no-div-regex": "off",
    "no-else-return": "error",
    "no-empty-function": "off",
    "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": "error",
    "no-implied-eval": "off",
    "no-invalid-this": "off", // meh
    "no-iterator": "error",
    "no-labels": ["error", { "allowLoop": true }],
    "no-lone-blocks": "error",
    "no-loop-func": "off",
    "no-magic-numbers": "off",
    "no-multi-spaces": "error",
    "no-multi-str": "error",
    "no-new": "error",
    "no-new-func": "error",
    "no-new-wrappers": "error",
    "no-octal": "error",
    "no-octal-escape": "error",
    "no-param-reassign": "off",
    "no-process-env": "error",
    "no-proto": "error",
    "no-redeclare": "error",
    "no-restricted-properties": "off",
    "no-return-assign": ["error", "except-parens"],
    "no-return-await": "error",
    "no-script-url": "off",
    "no-self-assign": "error",
    "no-self-compare": "error",
    "no-sequences": "error",
    "no-throw-literal": "error",
    "no-unmodified-loop-condition": "error",
    "no-unused-expressions": "error",
    "no-unused-labels": "error",
    "no-useless-call": "error",
    "no-useless-concat": "error",
    "no-useless-escape": "error",
    "no-useless-return": "error",
    "no-void": "error",
    "no-warning-comments": "off",
    "no-with": "error",
    "prefer-promise-reject-errors": "error",
    "radix": ["error", "as-needed"],
    "require-await": "error",
    "vars-on-top": "off",
    "wrap-iife": ["error", "outside"],
    "yoda": ["error", "never"],

    // Strict Mode
    "strict": ["error", "global"],

    // Variables
    "init-declarations": "off",
    "no-catch-shadow": "error",
    "no-delete-var": "error",
    "no-label-var": "error",
    "no-restricted-globals": "off",
    "no-shadow": "error",
    "no-shadow-restricted-names": "error",
    "no-undef": "error",
    "no-undef-init": "error",
    "no-undefined": "off",
    "no-unused-vars": "error",
    "no-use-before-define": ["error", "nofunc"],

    // Node.js and CommonJS
    "callback-return": "off",
    "global-require": "error",
    "handle-callback-err": "error",
    "no-buffer-constructor": "error",
    "no-mixed-requires": ["error", true],
    "no-new-require": "error",
    "no-path-concat": "error",
    "no-process-exit": "error",
    "no-restricted-modules": "off",
    "no-sync": "off",

    // Stylistic Issues
    "array-bracket-newline": ["error", { "multiline": true }],
    "array-bracket-spacing": ["error", "never"],
    "array-element-newline": ["off"],
    "block-spacing": ["error", "always"],
    "brace-style": ["error", "1tbs", { "allowSingleLine": false }],
    "camelcase": ["error", { "properties": "always" }],
    "capitalized-comments": "off",
    "comma-dangle": ["error", "never"],
    "comma-spacing": ["error", { "before": false, "after": true }],
    "comma-style": ["error", "last"],
    "computed-property-spacing": ["error", "never"],
    "consistent-this": "off",
    "eol-last": "error",
    "func-call-spacing": ["error", "never"],
    "func-name-matching": ["error"],
    "func-names": "off",
    "func-style": ["error", "declaration"],
    "function-paren-newline": ["error", "multiline"],
    "id-blacklist": "off",
    "id-length": "off",
    "id-match": "off",
    "indent": ["error", 2, { "SwitchCase": 1, "CallExpression": {"arguments": "first"}, "FunctionExpression": {"parameters": "first"}, "ignoredNodes": ["ConditionalExpression"] }],
    "jsx-quotes": "off",
    "key-spacing": ["error", { "beforeColon": false, "afterColon": true, "mode": "strict" }],
    "keyword-spacing": ["error", { "before": true, "after": true }],
    "line-comment-position": "off",
    "linebreak-style": ["error", "unix"],
    "lines-around-comment": "off",
    "max-depth": "off",
    "max-len": ["error", 120, { "ignoreUrls": true }],
    "max-lines": "off",
    "max-nested-callbacks": "off",
    "max-params": "off",
    "max-statements": "off",
    "max-statements-per-line": ["error", { "max": 1 }],
    "multiline-ternary": ["error", "always-multiline"],
    "new-cap": ["error", { "capIsNewExceptions": ["ByteString", "USVString", "DOMString"] }],
    "new-parens": "error",
    "newline-per-chained-call": "off",
    "no-array-constructor": "error",
    "no-bitwise": "off",
    "no-continue": "off",
    "no-inline-comments": "off",
    "no-lonely-if": "error",
    "no-mixed-operators": [
      "error",
      {
        "groups": [
          ["&", "|", "^", "~", "<<", ">>", ">>>"],
          ["==", "!=", "===", "!==", ">", ">=", "<", "<="],
          ["&&", "||"],
          ["in", "instanceof"]
        ]
      }
    ],
    "no-mixed-spaces-and-tabs": "error",
    "no-multi-assign": "off",
    "no-multiple-empty-lines": "error",
    "no-negated-condition": "off",
    "no-nested-ternary": "error",
    "no-new-object": "error",
    "no-plusplus": "off",
    "no-restricted-syntax": "off",
    "no-tabs": "error",
    "no-ternary": "off",
    "no-trailing-spaces": "error",
    "no-underscore-dangle": "off",
    "no-unneeded-ternary": "error",
    "no-whitespace-before-property": "error",
    "nonblock-statement-body-position": "error",
    "object-curly-newline": ["error", { "consistent": true }],
    "object-curly-spacing": ["error", "always"],
    "object-property-newline": "off",
    "one-var": ["error", "never"],
    "one-var-declaration-per-line": ["error", "initializations"],
    "operator-assignment": ["error", "always"],
    "operator-linebreak": ["error", "after"],
    "padded-blocks": ["error", "never"],
    "padding-line-between-statements": "off",
    "quote-props": ["error", "as-needed"],
    "quotes": ["error", "double", { "avoidEscape": true, "allowTemplateLiterals": true }],
    "require-jsdoc": "off",
    "semi": ["error", "always"],
    "semi-spacing": "error",
    "semi-style": "error",
    "sort-keys": "off",
    "sort-vars": "off",
    "space-before-blocks": ["error", "always"],
    "space-before-function-paren": ["error", { "anonymous": "always", "named": "never" }],
    "space-in-parens": ["error", "never"],
    "space-infix-ops": "error",
    "space-unary-ops": ["error", { "words": true, "nonwords": false }],
    "spaced-comment": ["error", "always", { "markers": ["///"] }],
    "switch-colon-spacing": "error",
    "template-tag-spacing": "error",
    "unicode-bom": "error",
    "wrap-regex": "off",

    // ECMAScript 6
    "arrow-body-style": "off", // meh
    "arrow-parens": ["error", "as-needed"],
    "arrow-spacing": "error",
    "constructor-super": "error",
    "generator-star-spacing": ["error", "after"],
    "no-class-assign": "error",
    "no-confusing-arrow": "off",
    "no-const-assign": "error",
    "no-dupe-class-members": "error",
    "no-duplicate-imports": "error",
    "no-new-symbol": "error",
    "no-restricted-imports": "off",
    "no-this-before-super": "error",
    "no-useless-computed-key": "error",
    "no-useless-constructor": "error",
    "no-useless-rename": "error",
    "no-var": "error",
    "object-shorthand": "error",
    "prefer-arrow-callback": "error",
    "prefer-const": ["error", { "ignoreReadBeforeAssign": true }],
    "prefer-destructuring": ["error", { "VariableDeclarator": { "array": false, "object": true }, "AssignmentExpression": { "array": false, "object": false } }, { "enforceForRenamedProperties": false }],
    "prefer-numeric-literals": "error",
    "prefer-rest-params": "off",
    "prefer-spread": "error",
    "prefer-template": "off",
    "require-yield": "error",
    "rest-spread-spacing": "error",
    "sort-imports": "off",
    "symbol-description": "error",
    "template-curly-spacing": ["error", "never"],
    "yield-star-spacing": ["error", "after"],

    // Custom rules
    "jsdom-internal/hook-super-invocation": ["error",
      { "ancestor": "NodeImpl", "hook": "_attach" },
      { "ancestor": "NodeImpl", "hook": "_detach" },
      { "ancestor": "NodeImpl", "hook": "_descendantAdded" },
      { "ancestor": "NodeImpl", "hook": "_descendantRemoved" },
      { "ancestor": "NodeImpl", "hook": "_childTextContentChangeSteps" },
      { "ancestor": "ElementImpl", "hook": "_attrModified" }
    ]
  },

  // Rules limited to specific locations
  "overrides": [
    {
      "files": ["lib/**"],
      "rules": {
        "no-restricted-properties": ["error",
          { "property": "getAttribute", "message": "Use 'getAttributeNS' with null as the namespace to access attributes within jsdom" },
          { "property": "setAttribute", "message": "Use 'setAttributeNS' with null as the namespace to access attributes within jsdom" },
          { "property": "hasAttribute", "message": "Use 'hasAttributeNS' with null as the namespace to access attributes within jsdom" },
          { "property": "removeAttribute", "message": "Use 'removeAttributeNS' with null as the namespace to access attributes within jsdom" },
          { "property": "toggleAttribute", "message": "Use 'setAttributeNS' and 'removeAttributeNS' with null as the namespace to access attributes within jsdom" }
        ]
      }
    }
  ]
}