I had the need to find the extension of a file.

I had the name of the file, in my case an image, and wanted to get the extension (.jpg, .png..).

To do this, you can use the path built-in module and its extname() method:

const path = require('path')

path.extname('picture.png') //.png
path.extname('picture.of.a.dog.png') //.png
path.extname('picture.of.a.dog.jpg') //.jpg
path.extname('picture.of.a.dog.jpeg') //.jpeg