Is There a Set Data Structure in JavaScript?


Angela Bailey

Is There a Set Data Structure in JavaScript?

In JavaScript, there is no built-in data structure called a “Set” like in other programming languages such as Python or Java. However, JavaScript provides an alternative way to work with sets using the Set object.

The Set Object

The Set object is a collection of unique values, allowing you to store any type of values – whether they are primitive values or object references. Each value within a set can only occur once, ensuring that there are no duplicates.

To create a new set in JavaScript, you can use the following syntax:

const mySet = new Set();

This creates an empty set called mySet. You can also initialize it with an iterable object such as an array:

const mySet = new Set([1, 2, 3]);
console.log(mySet); // Output: Set {1, 2, 3}

Working with Sets

Sets have several built-in methods that allow you to perform various operations. Here are some commonly used methods:

  • Add: Adds a new element to the set.
  • Delete: Removes an element from the set.
  • Has: Checks if an element exists in the set.
  • Size:Returns the number of elements in the set.
  • Clear: Removes all elements from the set.

Let’s see some examples:

// Creating a new set
const mySet = new Set();

// Adding elements to the set

// Checking if an element exists
console.log(mySet.has(2)); // Output: true

// Removing an element
console.has(2)); // Output: false

// Getting the size of the set
console.size); // Output: 2

// Clearing the set
console.size); // Output: 0

Iterating Over Sets

You can also iterate over sets using loops or built-in methods. The most common way is to use a for..of loop:

const mySet = new Set([1, 2, 3]);

for(const item of mySet){
// Output:
// 1
// 2
// 3

You can also convert a set to an array using the [.set] syntax:

const mySet = new Set([1, 2, 3]);
const myArray = [.mySet];
console.log(myArray); // Output: [1, 2, 3]

Differences with Other Data Structures

While sets in JavaScript can be used to perform similar operations as arrays or objects, they have some key differences:

  • Sets only store unique values, whereas arrays can contain duplicates.
  • Sets don’t have a specific order, so you can’t access elements using indexes like in arrays.
  • Sets provide built-in methods for set-specific operations such as union, intersection, and difference.

It’s important to consider these differences when deciding whether to use a set or another data structure in your JavaScript code.


Although JavaScript doesn’t have a built-in data structure called “Set,” the Set object provides a powerful alternative for working with sets. With its unique property and various built-in methods, you can efficiently handle collections of unique values in your JavaScript programs.

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