How to perform intersection of two sets in JavaScript ?

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An intersection of two sets means the element which occurs in both sets. In mathematical terms, the intersection of two sets is shown by A ∩ B. It means all the elements which is common in set A and set B should occur in a single array. In javascript, the intersection of two sets means getting the common from both sets.

We can find the intersection of two sets in many ways:

JavaScript Sets: Set can store any type of value whether primitive or objects.
JavaScript filter() Method: Create a new array from a given array consisting of only those elements from the given array which satisfy a condition set by the argument method.
JavaScript set.has() Method: Check whether an element with a specified value exists in a Set or not.

Using Sets & has() Method: A set is a collection of items that are unique i.e no element can be repeated. Set in ES6 are ordered: elements of the set can be iterated in the insertion order. A set can store any type of value whether primitive or objects.

Example 1: In this example, we will see the intersection of sets by using the set.has() method.

Javascript

function getIntersection(set1, set2) { 
    const ans = new Set(); 
    for (let i of set2) { 
        if (set1.has(i)) { 
            ans.add(i); 
        } 
    } 
    return ans; 
} 
const set1 = new Set([1, 2, 3, 8, 11]); 
const set2 = new Set([1, 2, 5, 8]); 
  
const result = getIntersection(set1, set2); 
console.log(result);

Output:

Set(3) { 1, 2, 8 }

Using the has() & filter() Method: We check if the element is present in set1 also then we are going to add that element to the new set.

Example 2: In this example, we will see the intersection of sets by using the filter() method. We have also used the spread operator for separating the element.

Javascript

let set1 = new Set([1, 2, 3]); 
let set2 = new Set([4, 3, 2]); 
let set = new Set([...set1].filter(x => set2.has(x))); 
console.log(set);

Output:

Set(2) { 2, 3 }

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