Math.random()

Summary

The Math.random() function returns a floating-point, pseudo-random number in the range [0, 1) that is, from 0 (inclusive) up to but not including 1 (exclusive), which you can then scale to your desired range.

The random number generator is seeded from the current time, as in Java.

Syntax

Math.random()

Parameters

None.

Examples

Example: Using Math.random

Note that as numbers in JavaScript are IEEE 754 floating point numbers with round-to-nearest-even behavior, these ranges, excluding the one for Math.random() itself, aren't exact, and depending on the bounds it's possible in extremely rare cases (on the order of 1 in 2⁶²) to calculate the usually-excluded upper bound.

// Returns a random number between 0 (inclusive) and 1 (exclusive)
function getRandom() {
  return Math.random();
}

// Returns a random number between min (inclusive) and max (exclusive)
function getRandomArbitrary(min, max) {
  return Math.random() * (max - min) + min;
}

// Returns a random integer between min (included) and max (excluded)
// Using Math.round() will give you a non-uniform distribution!
function getRandomInt(min, max) {
  return Math.floor(Math.random() * (max - min)) + min;
}

Specifications

Browser compatibility