# Check if a number is in a given range

Test an inclusive range whose ends may be given in any order, with an optional tolerance.

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

## Implementation

```javascript
function inRange({ value, a, b, threshold = 0 }) { return Math.min(a, b) - threshold <= value && value <= Math.max(a, b) + threshold; }
```

## Input

```json
{
  "value": 5,
  "a": 10,
  "b": 1
}
```

## Expected output

```json
true
```

## Edge case

Input:
```json
{
  "value": 10.5,
  "a": 1,
  "b": 10,
  "threshold": 0.5
}
```
Output:
```json
true
```

## Limits

- Both ends are included; threshold widens the range on both sides.

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-in-a-given-range.mdx
Author: Nguyen Huu Phuoc and original contributors
Contributors: See original repository history
Source commit: 14b481cf60dff1620ab1bb99a43b1f68068cdd9b
Copyright (c) 2020 phuoc-ng
License: MIT — https://1loc.dev/licenses/
Maintainer: Oveyon
Modifications: Takes named fields with an optional threshold. Original MDX retained as inert source evidence.