• 2 min

How To Create a Random String with JavaScript

How To Create a Random String with JavaScript
Table of Content

For many purposes, you can need a random string. Sometimes a long one and sometimes a short one. A lot of time, I use these functions in a unit or end-to-end test to automate even more.

In this post, I will show you how you can create it yourself; I will explain every part of the function to extend it yourself.

Enjoy the ride!

Get a random number

In JavaScript, we have a Math Object with all kinds of mathematical constants and functions. You need Math.random() when you want to create random things. This will return a random float. (Try it in your console). The result of this function is always higher than 0 and lower than 1.


But since we want to generate a short random string, we don’t need a number in the first place. By multiplying the result Math.random() * 10 you will get a number between 1 and not higher than 10. Our result could be 5.698829761336681 something like that.

Math.random() * 10 // returns 5.698829761336681

Convert random number into string

So how do we turn this into a string? Pretty simple, if you put .toString(36) behind this, you will get a string with numbers and letters with a dot in between. With the number 36 as a parameter in the .toString() method, you apply a base 36 encoding on the string.

;(Math.random() * 10).toString(36) // returns '9.ja773x85wr'

Replace dots in string

Every time you run this code, it will be different. If you want to remove the dot, then replace it like this.

;(Math.random() * 10).toString(36).replace('.', '') // returns '1cq54mxwg9hl'

Create randomString function

Now that you have generated a random string every time you run it, you can turn it into a function.

function randomString() {    return (Math.random() * 1000000).toString(36).replace('.', '')}

Generate longer random string

What are you want to have a longer string? You can create a loop and turn that into a string again.

function randomString() {    return [...Array(5)].map(value => (Math.random() * 1000000).toString(36).replace('.', '')).join('')}
randomString();// returns '8mtmvtuzzfnau0bf0ecy668tzrc3ztc57a7b87vehyu51yb8gj35t7'

I would recommend playing around with this function and using it for something practical.

The next post will be another JavaScript exercise.


After reading this post, I hope you learned something new or are inspired to create something new! 🤗

If I left you with questions or something to say as a response, scroll down and type me a message. Please send me a DM on Twitter @DevByRayRay when you want to keep it private. My DM’s are always open 😁


I’m Ray, a Frontend Developer since 2009 living in the Netherlands. I write about Frontend Development, JavaScript, TypeScript, Angular, CSS, VueJS and a lot more related topics.

Want to reach me for comments or questions on my blog? Send a DM on Twitter @DevByRayRay