random-uint-below.js

Usage

randomUIntBelow(max) returns a random non-negative integer less than max (0 <= output < max). max must be at most 2^53.

import {randomUIntBelow} from "random-uint-below"


console.log(randomUIntBelow(6)); // Generates a uniform random value from [0, 1, 2, 3, 4, 5]

Since one of the most comon use cases for this is to select a random element from an array, we also provide a convenience:

import {randomChoice} from "random-uint-below"

console.log(randomChoice(["vanilla", "strawberry", "peppermint"]))

Requirements

random-uint-below.js requires crypto.getRandomValues, which is available in:

• All major browsers since 2014: https://caniuse.com/getrandomvalues
• bun and deno
• node without a flag since v19: https://nodejs.org/api/webcrypto.html#cryptogetrandomvaluestypedarray
  • Available in earlier versions with the --experimental-global-webcrypto flag.

Builds are only published in ESM (with ES2020 compatibility).

License

MIT or GPL.