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# no-typeof-undefined

[Added in v0.9.5](https://github.com/web-infra-dev/rslint/releases/tag/v0.9.5)
## Configuration

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


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

export default defineConfig([
  unicornPlugin.configs.recommended,
  {
    rules: {
      'unicorn/no-typeof-undefined': 'error',
    },
  },
]);
```

Disallow comparing `undefined` using `typeof`.

Prefer a direct comparison:

```js
// Incorrect
if (typeof value === 'undefined') {
}

// Correct
if (value === undefined) {
}
```

By default, references that resolve to globals are ignored because removing
`typeof` can turn an existence check into a `ReferenceError`. Set
`checkGlobalVariables: true` to report those cases as suggestions instead of
autofixes.

This port follows eslint-plugin-unicorn v75.0.0, including converting
`==`/`!=` to strict equality, ASI-sensitive replacements, and multiline return/throw handling. Autofixes are intentionally withheld for the browser `document.all` legacy object, including binding-aware `globalThis`, `window`, `self`, `frames`, `top`, and `parent` Window aliases, because replacing `typeof … === 'undefined'` there would change runtime behavior.

- [Upstream documentation](https://github.com/sindresorhus/eslint-plugin-unicorn/blob/v75.0.0/docs/rules/no-typeof-undefined.md)
- [Upstream source](https://github.com/sindresorhus/eslint-plugin-unicorn/blob/v75.0.0/rules/no-typeof-undefined.js)