JavaScript Set

A set is collection of unique elements. That can contain any type of values or objects reference. The specialty of set object is that are contains a collection of unique (duplicate) element. There are many ways to create a set in Javascript.

new Set([iterable])

//Create an empty set
let first = new Set();

//Create set, which is store integer values
let second = new Set([1,2,3,4]); 

//Create a set, which are store the reference of other sets
let third = new Set([first,second]);

//Create a set, Which is created by String value
let fourth = new Set("JS");

//Discarding the repeated element
let fifth = new Set("AAAABBBCCC"); //Display ABC


console.log(first);
console.log(second);
console.log(third);
console.log(fourth);
console.log(fifth);

Set {}
Set { 1, 2, 3, 4 }
Set { Set {}, Set { 1, 2, 3, 4 } }
Set { 'J', 'S' }
Set { 'A', 'B', 'C' }

Method and attributes of Set

set.add(value)

This method are adding a new element into of a given set.

//Create an empty set
let fruit = new Set();

//Add new set element
fruit.add("Apple");
fruit.add("Banana");
fruit.add("Orange");

console.log(fruit);

Set { 'Apple', 'Banana', 'Orange' }

set.delete(value)

delete() method are remove given element from a set. When delete element are exist in set then this method are return true value otherwise returning false value.

//Create a set of 5 integer value
let element = new Set([1,2,3,4,5]); 
element.delete(4);
console.log(element);

element.delete(3);
console.log(element);

element.delete(5);
console.log(element);

//When element are not found
element.delete(7);
console.log(element);

Set { 1, 2, 3, 5 }
Set { 1, 2, 5 }
Set { 1, 2 }
Set { 1, 2 }

set.has(value)

//define set
let element = new Set([10,20,30]); 
//Check that set element are exist or not
console.log(element.has(10));
console.log(element.has(20));
console.log(element.has(100));
console.log(element.has(true));

true
true
false
false

set.size

//define set
let set1 = new Set([10,20,30,40,100]); 
let set2 = new Set(["one","two"]); 
//get the total elements of set
console.log(set1.size);
console.log(set2.size);

5
2

Iteration over Set

//define set
let element = new Set([1,2,3,4,5]); 
//iterating set element
element.forEach(function(data){
	console.log(data);
}); 

1
2
3
4
5

entries() method of set are returning a iterator of set elements.

//define set
let element = new Set([1,2,3,4,5]); 
let record = element.entries(); 
console.log(record);

console.log(record.next());
console.log(record.next());
console.log(record.next());
console.log(record.next());
console.log(record.next());
console.log(record.next());

[Set Iterator] { 1, 2, 3, 4, 5 }
{ value: [ 1, 1 ], done: false }
{ value: [ 2, 2 ], done: false }
{ value: [ 3, 3 ], done: false }
{ value: [ 4, 4 ], done: false }
{ value: [ 5, 5 ], done: false }
{ value: undefined, done: true }