eslint-flat-config-airbnb/base/variables.js

A mostly reasonable approach to JavaScript, updated for ESLint 9+

const confusingBrowserGlobals =  [
  "addEventListener", "blur", "close", "closed",
  "confirm", "defaultStatus", "defaultstatus", "event", 
  "external", "find", "focus", "frameElement", "frames", 
  "history", "innerHeight", "innerWidth", "length", "location", 
  "locationbar", "menubar", "moveBy", "moveTo", "name", "onblur",
  "onerror", "onfocus", "onload", "onresize", "onunload", "open", 
  "opener", "opera", "outerHeight", "outerWidth", "pageXOffset", 
  "pageYOffset", "parent", "print", "removeEventListener", "resizeBy",
  "resizeTo", "screen", "screenLeft", "screenTop", "screenX", "screenY", 
  "scroll", "scrollbars", "scrollBy", "scrollTo", "scrollX", "scrollY", 
  "self", "status", "statusbar", "stop", "toolbar", "top"
];

module.exports = {
  rules: {
    // enforce or disallow variable initializations at definition
    'init-declarations': 'off',

    // disallow the catch clause parameter name being the same as a variable in the outer scope
    'no-catch-shadow': 'off',

    // disallow deletion of variables
    'no-delete-var': 'error',

    // disallow labels that share a name with a variable
    // https://eslint.org/docs/rules/no-label-var
    'no-label-var': 'error',

    // disallow specific globals
    'no-restricted-globals': [
      'error',
      {
        name: 'isFinite',
        message:
          'Use Number.isFinite instead https://github.com/airbnb/javascript#standard-library--isfinite',
      },
      {
        name: 'isNaN',
        message:
          'Use Number.isNaN instead https://github.com/airbnb/javascript#standard-library--isnan',
      },
    ].concat(confusingBrowserGlobals.map((g) => ({
      name: g,
      message: `Use window.${g} instead. https://github.com/facebook/create-react-app/blob/HEAD/packages/confusing-browser-globals/README.md`,
    }))),

    // disallow declaration of variables already declared in the outer scope
    'no-shadow': 'error',

    // disallow shadowing of names such as arguments
    'no-shadow-restricted-names': 'error',

    // disallow use of undeclared variables unless mentioned in a /*global */ block
    'no-undef': 'error',

    // disallow use of undefined when initializing variables
    'no-undef-init': 'error',

    // disallow use of undefined variable
    // https://eslint.org/docs/rules/no-undefined
    // TODO: enable?
    'no-undefined': 'off',

    // disallow declaration of variables that are not used in the code
    'no-unused-vars': ['error', { vars: 'all', args: 'after-used', ignoreRestSiblings: true }],

    // disallow use of variables before they are defined
    'no-use-before-define': ['error', { functions: true, classes: true, variables: true }],
  }
};