---
url: /docs/guide/usage/linter/rules/unicorn/no-null.md
---

### What it does

Disallow the use of the `null` literal, to encourage using `undefined` instead.

### Why is this bad?

There are some reasons for using `undefined` instead of `null`.

* From experience, most developers use `null` and `undefined` inconsistently and interchangeably, and few know when to use which.
* Supporting both `null` and `undefined` complicates input validation.
* Using `null` makes TypeScript types more verbose: `type A = {foo?: string | null}` vs `type A = {foo?: string}`.

### Examples

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

```javascript
let foo = null;
```

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

```javascript
let foo;
```

## Configuration

This rule accepts a configuration object with the following properties:

### checkArguments

type: `boolean`

default: `true`

When set to `true`, disallow the use of `null` as a direct function call or constructor argument.

### checkStrictEquality

type: `boolean`

default: `false`

When set to `true`, the rule will also check strict equality/inequality comparisons (`===` and `!==`) against `null`.

## How to use

## Version

This rule was added in v0.0.21.

## References