#no-unused-vars

#Configuration

import { defineConfig, js } from '@rslint/core';

export default defineConfig([
  js.configs.recommended,
  {
    rules: {
      'no-unused-vars': 'error',
    },
  },
]);

#Rule Details

Disallow variables that are declared or assigned but never read. Removing unused bindings keeps scope intent clear and catches misspellings, incomplete refactors, and discarded assignments.

Examples of incorrect code for this rule:

const unused = 1;

function greet(name, punctuation) {
  return `Hello, ${name}`;
}

let result;
result = calculate();

Examples of correct code for this rule:

const value = calculate();
consume(value);

function greet(name) {
  return `Hello, ${name}`;
}

export const publicValue = 1;

The rule reports a discarded binding at its last write in the binding's variable scope. When it is safe to do so, the diagnostic includes a suggestion that removes the unused declaration, parameter, destructuring element, class, function, or import.

#Options

The rule accepts either "all" or "local" as a shorthand for vars, or one options object:

{
  "no-unused-vars": [
    "error",
    {
      "vars": "all",
      "args": "after-used",
      "caughtErrors": "all",
      "ignoreRestSiblings": false,
      "ignoreClassWithStaticInitBlock": false,
      "ignoreUsingDeclarations": false,
      "reportUsedIgnorePattern": false
    }
  ]
}

• vars: Check all variables ("all", the default) or only variables in non-global scopes ("local"). Top-level ES module bindings are local and remain checked.
• varsIgnorePattern: Ignore variable names matching this JavaScript regular expression.
• args: Check all parameters ("all"), only parameters after the last used parameter ("after-used", the default), or no parameters ("none").
• argsIgnorePattern: Ignore parameter names matching this JavaScript regular expression.
• caughtErrors: Check catch-clause bindings ("all", the default) or ignore them ("none").
• caughtErrorsIgnorePattern: Ignore catch-clause binding names matching this JavaScript regular expression.
• destructuredArrayIgnorePattern: Ignore direct array-destructuring elements that match this JavaScript regular expression. Defaulted and rest elements continue to use their ordinary variable, parameter, or catch-clause option.
• ignoreRestSiblings: Ignore direct object-destructuring properties that have a rest sibling. Bindings nested inside those properties are still checked.
• ignoreClassWithStaticInitBlock: Ignore classes containing a static initialization block.
• ignoreUsingDeclarations: Ignore using and await using declarations.
• reportUsedIgnorePattern: Report a binding when its name matches an ignore pattern but the binding is actually used.

For example, this configuration allows underscore-prefixed parameters:

{
  "no-unused-vars": ["error", { "args": "all", "argsIgnorePattern": "^_" }]
}

#The /* exported */ comment

A script shares its globals with the other scripts loaded alongside it, where this rule cannot see them being read. An /* exported name */ block comment declares that such a global is consumed elsewhere, and the rule counts the comment itself as a use:

/* exported publicValue */
var publicValue = 1;

The comment resolves each name only against the outer global scope. Whether a file has that scope is determined by its effective languageOptions.sourceType, not by the presence of import or export syntax. With flat config, omitting sourceType makes .js and .ts files modules even when they contain no module syntax, so the comment has no effect. Set sourceType: "script" for a shared script.

Module bindings, bindings in a JavaScript CommonJS wrapper, block bindings, and function locals are still reported. An exact, case-sensitive .cjs extension defaults to the CommonJS wrapper. TypeScript-flavoured files configured as commonjs retain a global program scope, so their top-level bindings can be marked by the comment.

#Original Documentation

• ESLint: no-unused-vars
• Source code