es-toolkit/docs/reference/predicate/isNil.md

# isNil

Checks if a given value is null or undefined.

This function tests whether the provided value is either `null` or `undefined`.
It returns `true` if the value is `null` or `undefined`, and `false` otherwise.

This function can also serve as a type predicate in TypeScript, narrowing the type of the argument to `null` or `undefined`.

## Signature

```typescript
function isNil(x: unknown): x is null | undefined;
```

## Examples

```typescript
import { isNil } from 'es-toolkit/predicate';

const value1 = null;
const value2 = undefined;
const value3 = 42;
const result1 = isNil(value1); // true
const result2 = isNil(value2); // true
const result3 = isNil(value3); // false
```