#no-shadow

#Configuration

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

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

Disallow variable declarations from shadowing variables declared in the outer scope.

#Rule Details

Shadowing occurs when a local variable shares the same name as a variable in its containing scope. Inside the inner scope, the outer variable becomes inaccessible, which can be a source of confusion.

Examples of incorrect code for this rule:

var a = 3;
function b() {
  var a = 10;
}

Examples of correct code for this rule:

var a = 3;
function b() {
  var c = 10;
}

#Options

#builtinGlobals

Shadowing a built-in global (for example Object, Array) is reported when this option is true. Default: false.

Configured languageOptions.globals and active /* global */ directives participate as built-in globals; an explicit "off" setting un-declares the name, so shadowing it is no longer reported.

{ "no-shadow": ["error", { "builtinGlobals": true }] }

function foo() {
  var Object = 0;
}

#hoist

Controls whether shadowing is reported before the outer declaration. Default: "functions".

• "functions": report only before function declarations.
• "all": always report, even when the outer declaration appears after the inner one.
• "never": never report before the outer declaration.
• "types": report when the outer declaration is a type (type or interface).
• "functions-and-types": report for both outer function declarations and type declarations.

#allow

Array of names for which shadowing is allowed. Default: [].

{ "no-shadow": ["error", { "allow": ["done"] }] }

#ignoreOnInitialization

Ignores shadowing inside the initializer of the outer declaration when it is called as a callback or IIFE. Default: false.

{ "no-shadow": ["error", { "ignoreOnInitialization": true }] }

#ignoreTypeValueShadow

Ignores shadowing between a value and a type of the same name (TypeScript). Default: true.

#ignoreFunctionTypeParameterNameValueShadow

Ignores shadowing for parameters declared inside a function type. Default: true.

#Original Documentation

https://eslint.org/docs/latest/rules/no-shadow