I don’t often store things in a Set in JavaScript, but maybe I should. The fact it will only store unique values makes it pretty handy.
One place I do currently use a Set is for the TagList in my 11ty-based personal website. I start by defining TagList as a new, empty Set. I then need to assemble all possible tags so iterate blog posts and for each add its associated tags to TagList. This means I can be sure that all duplicates will be removed automatically.
As you would imagine, Set has built-in methods for adding, deleting and iterating items. But if you need to do something beyond that, you can easily turn it into an array, for example by:
const myArray = [...mySet];
Also, browser support is pretty good. So although to date I’ve been safely confining my use to Node scripts for building my static site, I could probably be using it client-side, too.