Implementing Set functionality in JavaScript

Learn how to implement union ,intersection , difference , symmetricDifference in JavaScript.

The Set object lets you store unique values of any type, whether primitive values or object references.

Example

var array = [1,2,3,4,4,5];

var set = new Set(array);

set; // Set(5) {1, 2, 3, 4, 5} duplicates are removed

The detailed introduction to Set is provided here.

Set operations that we are going to implement

• Union → returns a new Set which has all the elements from both set.
• Intersection→ returns a new Set which has common elements in both set.
• Difference → Set A — Set B will return elements from Set A which are not in Set B .
• Symmetric Difference → Returns a new set , which is created from elements of Set A , which are not present in Set B and elements of Set B which are not present in Set A .

1. Union

The union method returns all elements from SetA and SetB ,

function union(setA, setB) {

    return new Set([...setA, ...setB]);
}

var setA = new Set([1,2,3,4,5]);

var setB = new Set([3,4,5,6]);

union(setA, setB); Set(6) {1, 2, 3, 4, 5, 6}

2. Intersection

The Intersection operation returns a new Set which has common elements in both set. We can find that by

• Loop through setA
• If element of setA present in setB , push to a new set

We can check if a Set has an element using has method in Set object.

function intersect(setA, setB) {
   var commonElements = new Set();

for (var elem of setB) {

        if (setA.has(elem)) {
commonElements.add(elem);
        }

   }

    return commonElements;
}

var setA = new Set([1,2,3,4,5]);

var setB = new Set([3,4,5,6]);

intersect(setA, setB); // Set(3) {3, 4, 5}

3 . Difference

Set A — Set B will return elements from Set A which are not in Set B , if we perform Set B — Set A then the function will return elements from Set B which are not present in Set A . We can achieve this by

• Loop through Set B and delete all elements of Set B in Set A using delete method in Set object

function difference(setA, setB) {

    var diff = new Set(setA);

    for (var elem of setB) {

        diff.delete(elem);

    }

    return diff;
}

var setA = new Set([1,2,3,4,5]);

var setB = new Set([3,4,5,6]);

// SET A - SET B

difference(setA, setB); // Set(3) {1,2}

// SET B- SET A

difference(setB, setA); // Set(3) {6}

4. Symmetric Difference

This method returns a new set , which is created from elements of Set A , which are not present in Set B and elements of Set B which are not present in Set A . We can achieve this by

• Create a new set Result Set from Set A

For each Element of Set B

• If the element of Set B present in Result Set then remove it .
• If the element is not present then add to the Result Set

function symmetricDifference(setA, setB) {

    var resultSet = new Set(setA);

    for (var elem of setB) {

        if (resultSet.has(elem)) {

           resultSet.delete(elem);
        } else {

           resultSet.add(elem);
        }
    }
    return resultSet;
}

var setA = new Set([1,2,3,4,5]);

var setB = new Set([3,4,5,6]);

symmetricDifference(setA, setB); // Set(3) {1, 2, 6}

5. isSuperSet

This is a util function which will check of all elements on subset present in Set . We can achieve this by

For each element of subset

• if any element is not present in set return false.

function isSuperset(set, subset) {

    for (var elem of subset) {

        if (!set.has(elem)) {
            return false;
        }

    }

    return true;
}

var set = new Set([1,2,3,4]);

var subset = new Set([3,4]);

isSuperset(set, subset); // true

subset = new Set([3,4,6]);

isSuperset(set, subset); // false

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