#no-inner-declarations

#Configuration

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

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

#Rule Details

Disallow variable and/or function declarations outside the root of a program, function body, or class static block body. With the "both" option, this also applies to var declarations in for, for-in, and for-of headers. It does not apply to let, const, using, or await using, which are block-scoped.

By default, nested function declarations are allowed only when the code is in strict mode and languageOptions.ecmaVersion is 2015 or newer. Use the blockScopedFunctions option to disallow them in those contexts too.

Examples of incorrect code for this rule with the default options in a non-strict script:

if (test) {
  function doSomething() {}
}

Examples of incorrect code for this rule with { blockScopedFunctions: "disallow" }:

{
  "no-inner-declarations": [
    "error",
    "functions",
    { "blockScopedFunctions": "disallow" }
  ]
}

"use strict";

if (test) {
  function doSomething() {}
}

while (test) {
  function doSomething() {}
}

Examples of correct code for this rule with the default options:

function doSomething() {}

function doSomethingElse() {
  function doAnotherThing() {}
}

"use strict";

if (test) {
  function doSomething() {}
}

export function foo() {}

Examples of incorrect code for this rule with the "both" option:

{ "no-inner-declarations": ["error", "both"] }

if (test) {
  var x = 1;
}

function doSomething() {
  if (test) {
    var x = 1;
  }
}

for (var i = 0; i < items.length; i++) {}

for (var key in object) {}

for (var value of values) {}

Examples of correct code for this rule with the "both" option:

{ "no-inner-declarations": ["error", "both"] }

var x = 1;

function doSomething() {
  var y = 2;
}

if (test) {
  let x = 1;
}

for (const value of values) {}

#Options

• "functions" (default): Only disallows function declarations in nested blocks (when blockScopedFunctions is "disallow").
• "both": Disallows both function declarations (when blockScopedFunctions is "disallow") and var declarations in nested blocks.
• { blockScopedFunctions: "allow" | "disallow" } (default "allow"): With "allow", nested function declarations are permitted only in strict code when languageOptions.ecmaVersion is 2015 or newer. With "disallow", they are always checked.

#Original Documentation

• ESLint: no-inner-declarations
• Source code