JavaScript Set intersection With Two Different Ways

In This article, we will learn javascript set intersection with 2 different methods. 

what is an Intersection?

In mathematical terms, this is expressed as an Intersection A ∩ B creates a set that contains those elements of a set A that is also in the set B. in simple words Intersection means elements common in both “A” and “B”.

Step to get the intersection of Sets

1. Convert the first Set into an array.
2. Use the filter() method to iterate over the array.
3. Use the has() method to check if each value is contained in the second Set.
4. Convert the array back to a Set.

Method 1: JavaScript Set intersection

let a = new Set([1,2,3]);
let b = new Set([4,3,2]);

let intersection = new Set(
    [...a].filter(x => b.has(x))
);

console.log(intersection); // Output: { 2, 3 }

Explanation:

Here We used the ES6 spread syntax (…) to convert the first Set to an array.

console.log([...a]); // [ 1, 2, 3 ]

After we use the filter() method to iterate over the array. On each iteration.

The filter() method creates a new array with satisfying the provided condition

we call the Set.has method to check if the value is contained in the second Set.

The has() method returns true if the value is found in the Set, and false otherwise.

In last we use Set() constructor to convert the array back to a Set.

Method 2: JavaScript Set intersection

Here you can also achieve the same thing using a loop over one of the Set objects, and check which elements are common between the two by using the has() method on the other Set. For example:

const setA = new Set([1, 2, 3]);
const setB = new Set([4, 3, 2, 6]);

const result = new Set();

for (const elem of setA) {
    if (setB.has(elem)) {
        result.add(elem);
    }
}

console.log(result); // Set(2) {2, 3}

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