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Javascript Random String Fastest Way to Generate Random Strings in JavaScript

oyetoket profile image Oyetoke Toby Updated on ・2 min read

There are so many ways to generate random strings in JavaScript and it doesn't really matter which method is faster.

The method I like using most is Math.random()

I made a video on it:

Basically the idea is to use Math.random(), then you can convert it to string and do some simple string manipulation on it.

To get random numbers, I would use something like below:


To get random strings with numbers only, I would use:

Math.random().toString().substr(2, 5)

Fortunate .toString() has a param called radix that you can pass in numbers between 2 - 36 which will cast the generated numbers to the radix characters that fall between the given number. The radix is also known as base and its for representing numeric values

To get a random number between 0-1:

Math.random().toString(2).substr(2, 5)

To get a random number between 0-5:

Math.random().toString(5).substr(2, 5)

Starting from 11/12, it will start introducing letters. So to get a fully random string:

Math.random().toString(20).substr(2, 6)

With this you can now write your awesome random string generator:

const generateRandomString = function(){
return Math.random().toString(20).substr(2, 6)

To be able to change the length of the output:

const generateRandomString = function(length=6){
return Math.random().toString(20).substr(2, length)

One liner

const generateRandomString = (length=6)=>Math.random().toString(20).substr(2, length)

That's all.

If you know of any other faster ways, please I would love to see it in the comment section.


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oyetoket profile

Oyetoke Toby


Just a software engineer trying to make ends meet. My passion for Python and JavaScript is nothing to compare.


Editor guide

Nice function! But one thing I noticed is that this will only work for random alpha-numeric strings up to a certain length. If you want to have something longer, you should call the method recursively. Something like:

const generateRandomString = function (length, randomString="") {
  randomString += Math.random().toString(20).substr(2, length);
  if (randomString.length > length) return randomString.slice(0, length);
  return generateRandomString(length, randomString);

Hi, thanks for the simple, straight-forward article! I just wanted to point out a small error in your one-liner. You define the length variable, but you still used a hard-coded "6" instead of it in the expression.


Do you like base20 for something special?


No reason actually, I just like using it.