---
title: isUndefined
tags: type,beginner
firstSeen: 2018-01-16T16:50:21+02:00
lastUpdated: 2020-10-20T23:02:01+03:00
---

Checks if the specified value is `undefined`.

- Use the strict equality operator to check if `val` is equal to `undefined`.

```js
const isUndefined = val => val === undefined;
```

```js
isUndefined(undefined); // true
```