#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 in nested blocks. Function declarations and, optionally, variable declarations (var) should only appear at the root level of a program or the body of a function. This does not apply to let or const, which are block-scoped by design.

By default, function declarations in blocks are allowed because they are valid in ES2015+ strict mode (block-scoped). Use the blockScopedFunctions option to disallow them.

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

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() {}
}

// Block-scoped functions are allowed by default
if (test) {
  function doSomething() {}
}

export function foo() {}

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

if (test) {
  var x = 1;
}

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

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

var x = 1;

function doSomething() {
  var y = 2;
}

if (test) {
  let x = 1;
}

#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"): Controls whether function declarations inside blocks are reported. When "allow" (default), block-scoped function declarations are permitted as they are valid in ES2015+ strict mode.

#Original Documentation

https://eslint.org/docs/latest/rules/no-inner-declarations