The Underused Power of JavaScript Sets

Unlocking Unique Value Handling

Photo by Jessica Ruscello on Unsplash

Working with unique values is common in programming. You may need to remove duplicates from an array, check if a value already exists, or operate on a collection of unique items.

JavaScript has a built-in Set object that handles unique values elegantly, yet it often gets overlooked. In this post let’s explore some great ways to put JavaScript Sets to work!

Creating JavaScript Sets

A Set can be initialized from any iterable object, like an array:

const ids = new Set([1, 2, 2, 3]);
// ids = Set(3) {1, 2, 3}

Notice duplicates are automatically removed! We can also create an empty set:

const ids = new Set();

And insert values with .add():

ids.add(4); 
// ids = Set(4) {1, 2, 3, 4}

Checking Existence

A key use of sets is quickly checking value existence. The .has() method checks for membership:

ids.has(2);
// true

This provides O(1) lookups versus O(N) searching arrays!

Deleting & Clearing