Generate a random sign

Return 1 or -1 with equal probability.

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

function randomSign() { return Math.random() < 0.5 ? -1 : 1; }

Usage

const signs = Array.from({ length: 1000 }, randomSign);
signs.every(sign => sign === 1 || sign === -1); // → true
new Set(signs).size; // → 2

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

• Multiply by a magnitude for symmetric noise: randomSign() * magnitude.

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.