# Generate a weighted random number in given range

Return an integer in [min, max) skewed toward min.

Canonical: https://1loc.dev/random/generate-a-weighted-random-number-in-given-range/
Version: 1.0.0
Runtime: JavaScript · Node.js 22 / modern browsers
Verification: Usage lines executed in Node.js 22 and headless Chromium; no external services
Updated: 2026-10-28

## Implementation

```javascript
function weightedRandom(min, max) { return Math.floor(Math.random() ** 2 * (max - min)) + min; }
```

## Usage

```javascript
const draws = Array.from({ length: 10000 }, () => weightedRandom(0, 10));
draws.every(n => n >= 0 && n < 10); // → true
draws.filter(n => n < 5).length > draws.filter(n => n >= 5).length; // → true
```

Lines marked → were executed in Node.js 22 and in headless Chromium, and each result was compared with the value shown. Lines marked e.g. are illustrative.

## Limits

- Squaring a uniform number skews results toward min: about 71% of draws land in the lower half, which the example checks. max is excluded.
- For explicit weights per outcome, pick from a table of cumulative weights instead.

The function does not validate its arguments. Add checks where it receives untrusted input.

## Source and license

Original: https://github.com/phuocng/1loc/blob/14b481cf60dff1620ab1bb99a43b1f68068cdd9b/contents/generate-a-weighted-random-number-in-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: Documented as a reference with executed usage lines. Original MDX retained as inert source evidence.