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How to add leading zero to a number in JavaScript

Published Sep 23 2022

I had the need to add a leading zero when the number I had was less than 10, so instead of printing “9” on the screen, I had “09”.

The use case being I wanted to display the length of a video, and 5:04 is more logical than 5:4 to say a video is 5 minutes and 4 seconds.

Here’s how I did it:

Math.floor(mynumber)
    .toString()
    .padStart(2, '0')

All of this is native to JavaScript, using the Math built-in library



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