# How to merge sets - JavaScript

In this article we will learn how to merge sets in JavaScript.

It is very common to merge sets in JavaScript in JavaScript.

## Problem

Now we have a problem which is that we want to merge sets.

Now let's imagine that we have an `Set` with a set of numbers like this:

``````const set1 = new Set([1, 2, 3]);
const set2 = new Set([4, 5, 6]);
``````

And we want to merge two of them, to became output like this:

``````Set(6) { 1, 2, 3, 4, 5, 6 }
``````

How to solve this problem?

To solve this problem, we can use more than one method, such as:

• Using spread operator `...`.
• Using `concat` method.

## Merge two sets using spread operator `...`

We can use spread operator to merge two sets in JavaScript.

Let's see an example

``````// Sets
const set1 = new Set([1, 2, 3]);
const set2 = new Set([4, 5, 6]);

// Merge two sets
const set3 = new Set([...set1, ...set2]);
``````

Output

``````Set(6) { 1, 2, 3, 4, 5, 6 }
``````

## Merge two sets using `concat` method

We can use `concat` method to solve this problem as well.

But we should convert sets to arrays first and then use `concat` method.

Example

``````// Sets
const set1 = new Set([1, 2, 3]);
const set2 = new Set([4, 5, 6]);

// Convert to array
const toArr1 = Array.from(set1);
const toArr2 = Array.from(set2);

// Concat two arrays
const merge = toArr1.concat(toArr2);

// Convert to set
const set3 = new Set(merge);

// Result:
console.log(set3);
``````

Output

``````Set(6) { 1, 2, 3, 4, 5, 6 }
``````