How to Generate Random Number in a Specified Range in JavaScript

1. Math.random() Function
2. Algorithm to Generate Random Number in a Specified Range in JavaScript
3. Example Code

This tutorial introduces how to generate random numbers inside a specified range in JavaScript. We will use the Math.random() function to generate random numbers and then shift them to a number inside the specified range.

Math.random() Function

This function returns a floating-point, pseudo-random number in the range 0 (inclusive) to 1 (exclusive) with an approximately uniform distribution over that range. But it doesn’t return cryptographically secure numbers.

Algorithm to Generate Random Number in a Specified Range in JavaScript

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• Generate a number between the range 0 and 1 and store it in a variable named rand.

• Calculate the total range range as max-min+1.

• Multiply range by rand and add it to min to get the random number inside the specified range.

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Example Code

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

getRandomIntInclusive(2, 5);

Output:

4