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

Code Snippets - Generate a random number between two numbers in JavaScriptPhoto by
By Hemerson Carlin
1 min read

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:

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.

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. 👋🏼

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mersocarlin

Hemerson Carlin, also known as mersocarlin, is passionate and resourceful full-stack Software Engineer with 10+ years of experience focused on agile development, architecture and team building.

This is the space to share the things he likes, a couple of ideas and some of his work.

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