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