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# no-unassigned-vars

[Added in v0.6.5](https://github.com/web-infra-dev/rslint/releases/tag/v0.6.5)
## Configuration

| Preset                   | Configured Value |
| ------------------------ | ---------------- |
| ✅ js.configs.recommended | `"error"`        |


```ts title=rslint.config.ts
import { defineConfig, js } from '@rslint/core';

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

## Rule Details

This rule reports `let` and `var` variables that are read but never assigned a
value. These variables are always `undefined`, so reading them is usually a
programming mistake.

Examples of **incorrect** code for this rule:

```javascript
let status;
if (status === "ready") {
  console.log("Ready!");
}

let user;
greet(user);

function test() {
  let error;
  return error || "Unknown error";
}
```

Examples of **correct** code for this rule:

```javascript
let message = "hello";
console.log(message);

let user;
user = getUser();
console.log(user.name);

let temp;
```

Examples of **correct** TypeScript code for this rule:

```typescript
declare let value: number | undefined;
console.log(value);

declare module "my-module" {
  let value: string;
  export = value;
}
```

## Options

This rule has no options.

## Original Documentation

- [ESLint: no-unassigned-vars](https://eslint.org/docs/latest/rules/no-unassigned-vars)
- [Source code](https://github.com/eslint/eslint/blob/v10.8.1/lib/rules/no-unassigned-vars.js)