In this article, we would be discussing the Set object provided by ES6. 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. Set can store any type of value whether primitive or objects.
Syntax:
new Set([it]);
Parameter:
- it: It is an iterable object whose all elements are added to the new set created, If the parameter is not specified or null is passed then a new set created is empty.
Returns: A new set object
Example:
Javascript
let set1 = new Set(["sumit","sumit","amit","anil","anish"]);
let set2 = new Set("fooooooood");
let set3 = new Set([10, 20, 30, 30, 40, 40]);
let set4 = new Set();
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Properties:
Set.size – It returns the number of elements in the Set.
Methods of Set:
Set.add() – It adds the new element with a specified value at the end of the Set object.
Syntax:
set1.add(val);
Parameter:
- val: It is a value to be added to the set.
Return value: The set object
Example:
Javascript
let set1 = new Set();
set1.add(10);
set1.add(20);
set1.add(30).add(40).add(50);
console.log(set1);
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Output:
Set(5) {10, 20, 30, 40, 50}Set.delete() – It deletes an element with the specified value from the Set object.
Syntax:
set1.delete(val);
Parameter:
- val: It is a value to be deleted from the set.
Return value: true if the value is successfully deleted from the set else returns false.
Example:
Javascript
let set1 = new Set("foooodiiiieee");
console.log(set1.delete('e'));
console.log(set1);
console.log(set1.delete('g'));
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Output:
true
Set(4) {'f', 'o', 'd', 'i'}
falseSet.clear() – It removes all the element from the set.
Syntax:
set1.clear();
Parameter: This method does not take any parameter
Return value: Undefined
Example:
Javascript
let set2 = new Set([10, 20, 30, 40, 50]);
console.log(set2);
set2.clear()
console.log(set2);
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Output:
Set(5) {10, 20, 30, 40, 50}
Set(0) {size: 0}Set.entries() – It returns an iterator object which contains an array having the entries of the set, in the insertion order.
Syntax:
set1.entries();
Parameter: This method does not take any parameter
Return value: It returns an iterator object that contains an array of [value, value] for every element of the set, in the insertion order.
Example:
Javascript
let set1 = new Set();
set1.add(50);
set1.add(30);
set1.add(40);
set1.add(20);
set1.add(10);
let getEntriesArry = set1.entries();
console.log(getEntriesArry.next().value);
console.log(getEntriesArry.next().value);
console.log(getEntriesArry.next().value);
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Output:
(2) [50, 50]
(2) [30, 30]
(2) [40, 40]
Set.has() – It returns true if the specified value is present in the Set object.
Syntax:
set1.has(val);
Parameter:
- val: The value to be searched in the Set
Return value: True if the value is present else it returns false.
Example:
Javascript
let set1 = new Set();
set1.add(50);
set1.add(30);
console.log(set1.has(50));
console.log(set1.has(10));
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Output:
true
false
Set.values() – It returns all the values from the Set in the same insertion order.
Syntax:
set1.values();
Parameter: This method does not take any parameter
Return value: An iterator object that contains all the values of the set in the same order as they are inserted.
Set.keys(): It also returns all the values from the Set in the insertion order.
Note: It is similar to the values() in the case of Sets
Syntax:
set1.keys();
Parameter: This method does not take any parameter
Returns: An iterator object that contains all the values of the set in the same order as they are inserted.
Example:
Javascript
let set1 = new Set();
set1.add(50);
set1.add(30);
set1.add(40);
set1.add("Geeks");
set1.add("GFG");
let getValues = set1.values();
console.log(getValues);
let getKeys = set1.keys();
console.log(getKeys);
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Output:
SetIterator {50, 30, 40, 'Geeks', 'GFG'}
SetIterator {50, 30, 40, 'Geeks', 'GFG'}Set.forEach(): It executes the given function once for every element in the Set, in the insertion order.
Syntax:
set1.forEach(callback[,thisargument]);
Parameter:
- callback – It is a function that is to be executed for each element of the Set.
- The callback function is provided with three parameters as follows:
- the element key
- the element value
- the Set object to be traversed
- thisargument – Value to be used as this when executing the callback.
Return value: Undefined
Set.prototype[@@iterator](): It returns a Set iterator function which is values() function by default.
Syntax:
set1[Symbol.iterator]();
Parameter: This method does not take any parameter
Return value: A Set iterator function and it is values() by default.
Example:
Javascript
let set1 = new Set(["sumit","sumit","amit","anish"]);
let getit = set1[Symbol.iterator]();
console.log(getit.next());
console.log(getit.next());
console.log(getit.next());
console.log(getit.next());
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Output:
{value: 'sumit', done: false}
{value: 'amit', done: false}
{value: 'anish', done: false}
{value: undefined, done: true}Set Operations:
JavaScript subSet() Method: It returns true if Set A is a subset of Set B. A Set A is said to be a subset of Set B, if all the elements of Set A is also present in Set B. Now lets implement and use the subset function.
Example:
Javascript
Set.prototype.subSet = function(otherSet)
{
if(this.size > otherSet.size)
return false;
else
{
for(let elem of this)
{
if(!otherSet.has(elem))
return false;
}
return true;
}
}
let setA = new Set([10, 20, 30]);
let setB = new Set([50, 60, 10, 20, 30, 40]);
let setC = new Set([10, 30, 40, 50]);
console.log(setA.subSet(setB));
console.log(setA.subSet(setC));
console.log(setC.subSet(setB));
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Output:
true
false
true
JavaScript union() Method: It returns a Set which consists of the union of Set A and Set B. A Set is said to be a union of two sets, if it contains all elements of Set A as well as all elements of Set B, but it doesn’t contain duplicate elements.
If an element is present in both Set A and Set B then the union of Set A and B will contain a single copy of the element. Let’s implement and use the union function
Example:
Javascript
Set.prototype.union = function(otherSet)
{
let unionSet = new Set();
for (let elem of this)
{
unionSet.add(elem);
}
for(let elem of otherSet)
unionSet.add(elem);
return unionSet;
}
let set1 = new Set([10, 20, 30, 40, 50]);
let set2 = new Set([40, 50, 60, 70, 80]);
let unionSet = set1.union(set2);
console.log(unionSet.values());
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Output:
SetIterator {10, 20, 30, 40, 50, …}JavaScript intersection() Method: It returns the intersection of Set A and Set B. A Set is said to be the intersection of Set A and B if contains an element which is present both in Set A and Set B. Let’s implement and use the intersection function
Example:
Javascript
Set.prototype.intersection = function(otherSet)
{
let intersectionSet = new Set();
for(let elem of otherSet)
{
if(this.has(elem))
intersectionSet.add(elem);
}
return intersectionSet;
}
let set1 = new Set([10, 20, 30, 40, 50]);
let set2 = new Set([40, 50, 60, 70, 80]);
let intersectionSet = set1.intersection(set2);
console.log(intersectionSet.values());
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Output:
SetIterator {40, 50}JavaScript difference() Method: It returns the Set which contains the difference between Set A and Set B. A Set is said to be a difference between Set A and B if it contains set of elements e which are present in Set A but not in Set B. Let’s implement and use the difference function
Example:
Javascript
Set.prototype.difference = function(otherSet)
{
let differenceSet = new Set();
for(let elem of this)
{
if(!otherSet.has(elem))
differenceSet.add(elem);
}
return differenceSet;
}
let set1 = new Set([10, 20, 30, 40, 50]);
let set2 = new Set([40, 50, 60, 70, 80]);
let differenceSet = set1.difference(set2);
console.log(differenceSet);
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Output:
Set(3) {10, 20, 30}JavaScript is best known for web page development but it is also used in a variety of non-browser environments. You can learn JavaScript from the ground up by following this JavaScript Tutorial and JavaScript Examples.