javascript (ES6): Why do we need sets?

Question

My question is why do we need sets in ES6 and what is their actual difference from an array of strings? Can you define an example where a set is more accurate than an array of strings? I get it that maps save you the trouble of messing with objects, but sets just seem to serve no purpose.

Answer 1

The purpose of a Set is to enforce uniqueness. If the value you try to put in there already exists, then you will still just have one entry, not two like you would when pushing to an array. Additionally, trying to check if a set contains a certain element is a quick operation (constant time, aka O(1)), while trying to do the same with an array is slower (linear time, aka O(N)).