Code Snippets - Generate a random number between two numbers in JavaScript

This is another blog post I write about code snippets I find useful. Below is the list of the previous code snippets I have written about:

• Sort array of objects by a property in JavaScript
• Unique array in JavaScript
• Pre-populate an array in JavaScript
• uniqueId

Today's code snippet is about how to generate a random number between two numbers in JavaScript.

I usually go for this snippet in two main scenarios:

• When prototyping a UI without an endpoint: I like to randomize stats so I don't always get to see the same results over and over.
• Unit tests so I don't create biased tests: this is how I ensure reliability for tests that need some sort of number input. It's also helpful when I need to quickly create an array and its size doesn't really matter much.

Math.random gets us halfway through there: it returns a floating-point number between 0 and 1 (exclusive).

The next step is to use Math.random so it returns the number within the desired range:

/**
 * Generates a random number between @min (inclusive) and @max (exclusive)
 */
function generateRandomNumber(min: number, max: number) {
  Math.floor(Math.random() * (max - min) + min)
}

Should you need to a random number that could also be equal to max we'd have to add a + 1 to the difference between max and min:

/**
 * Generates a random number between @min (inclusive) and @max (inclusive)
 */
function generateRandomNumber(min: number, max: number) {
  return Math.floor(Math.random() * (max - min + 1)) + min
}

I hope that's helpful and interesting to you. 👋🏼