Random Number Generator

Math.random()

It is the Math.random() function returns a floating-point pseudo-random number in the range 0 to below 1 (inclusive of 0, but not exactly 1) with approximately an even distribution over that area -- which you could then scale to your desired range. The implementation selects the initial seed to the random number generation algorithm; it cannot be chosen or reset by the user.https://interactive-examples.mdn.mozilla.net/pages/js/math-random.html

Note: Math.random() does not provide cryptographicall ysecure random numbers. Avoid using them in connection with security. Use the Web Crypto API instead, and more precisely the window.crypto.getRandomValues() method.

Syntax

Math.random()

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Value of Return

A floating-point virtual random number between the numbers 0 (inclusive) to one (exclusive).

Examples

Note that as numbers in JavaScript are IEEE 754 floating point numbers with round-to-nearest-even behavior, the ranges claimed for the functions below (excluding the one for Math.random() itself) aren't exact. If extremely high boundaries are set (2^53 or greater), it's possible in very extremely rare situations to calculate the usually-excluded upper bound.

Finding a random number between 0 (inclusive) and 1 (exclusive)

function getRandom()  return Math.random();  

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Finding an random numberbetween two values

This example will return an random number between the specified values. The result isn't less than (and could possibly be greater than) min, and is less than (and less than) max.

function getRandomArbitrary(min, max)  return Math.random() * (max - min) + min;  

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Finding a random integer that is between two values

This code returns an indeterminate integer that is between the values specified. The value cannot be lower than min (or the next number larger by min in the event that min isn't an integer) as well as less than (but not exactly equal to) max.

function getRandomInt(min, max)  min = Math.ceil(min); max = Math.floor(max); return Math.floor(Math.random() * (max - min) + min); //The maximum is exclusive and the minimum is inclusive  

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Notice: It might be tempting to use Math.round() to accomplish that, but using this method could result in that your random numbers to have a different distribution, which might not be acceptable for your requirements.

The process of generating a random integer between two values inclusive

While the findRandomInt() function above is inclusive at the minimum, it's exclusive when you go to the maximum. What happens if you require the results to be inclusive at both the minimum and maximum? The getRandomIntInclusive() function below accomplishes that.

function getRandomIntInclusive(min, max)  min = Math.ceil(min); max = Math.floor(max); return Math.floor(Math.random() * (max - min + 1) + min); //The maximum is inclusive and the minimum is inclusive