# Check if a number is negative

Return true for numbers below zero.

Canonical: https://1loc.dev/validator/check-if-a-number-is-negative/
Version: 1.0.0
Runtime: JavaScript · Node.js 22 / modern browsers
Verification: Local fixtures; no external services
Updated: 2026-10-28

## Implementation

```javascript
function isNegative(n) { return n < 0; }
```

## Input

```json
-3
```

## Expected output

```json
true
```

## Edge case

Input:
```json
0
```
Output:
```json
false
```

## Limits

- -0 is not negative here, matching n < 0.

The lab validates types and size before calling this function. Add equivalent validation at your own trust boundary.

## Source and license

Original: https://github.com/phuocng/1loc/blob/14b481cf60dff1620ab1bb99a43b1f68068cdd9b/contents/check-if-a-number-is-negative.mdx
Author: Nguyen Huu Phuoc and original contributors
Contributors: sadirde, tugsanunlu
Source commit: 14b481cf60dff1620ab1bb99a43b1f68068cdd9b
Copyright (c) 2020 phuoc-ng
License: MIT — https://1loc.dev/licenses/
Maintainer: Oveyon
Modifications: Keeps the n < 0 variant. Original MDX retained as inert source evidence.