Generate a random integer in given range

Return an integer from min to max, both included.

JavaScriptNode.js & browsers Version 1.0.0 · MIT · .md

function randomInteger(min, max) { return Math.floor(Math.random() * (max - min + 1)) + min; }

Usage

const rolls = Array.from({ length: 1000 }, () => randomInteger(1, 3));
rolls.every(n => [1, 2, 3].includes(n)); // → true
new Set(rolls).size; // → 3

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.

Know the limits

• min and max must be integers. Both ends are included.
• For security-sensitive numbers, such as verification codes, use crypto.getRandomValues with rejection sampling, as in Generate a random string from given characters.

The function above is the code the usage lines run. It does not validate its arguments; add checks where it receives untrusted input.

Keep exploring

• Generate a random boolean — Return true or false with equal probability.
• Generate a random floating point number in given range — Scale Math.random into [min, max).
• Generate a random hex color — Return a #rrggbb color from 24 random bits.