#no-undef-init

#Configuration

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

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

#Rule Details

Disallow initializing variables to undefined.

In JavaScript, a variable that is declared and not initialized to any value automatically gets the value of undefined. It's therefore unnecessary to initialize a variable to undefined.

This rule aims to eliminate var and let variable declarations that initialize to undefined.

Examples of incorrect code for this rule:

var foo = undefined;
let bar = undefined;

Examples of correct code for this rule:

var foo;
let bar;
const baz = undefined;

#Differences from ESLint

The autofix preserves TypeScript type annotations and definite assignment tokens. ESLint's fix removes from the end of the variable name to the end of the declarator, which in TypeScript would also remove any type annotation:

// ESLint autofix: let a: string = undefined; → let a;  (type annotation lost)
// rslint autofix: let a: string = undefined; → let a: string;  (type annotation preserved)

#Original Documentation

https://eslint.org/docs/latest/rules/no-undef-init