Tutorials References Exercises Menu
Paid Courses

JS Tutorial

JS HOME JS Introduction JS Where To JS Output JS Statements JS Syntax JS Comments JS Variables JS Let JS Const JS Operators JS Arithmetic JS Assignment JS Data Types JS Functions JS Objects JS Events JS Strings JS String Methods JS String Search JS String Templates JS Numbers JS Number Methods JS Arrays JS Array Methods JS Array Sort JS Array Iteration JS Array Const JS Dates JS Date Formats JS Date Get Methods JS Date Set Methods JS Math JS Random JS Booleans JS Comparisons JS Conditions JS Switch JS Loop For JS Loop For In JS Loop For Of JS Loop While JS Break JS Typeof JS Type Conversion JS Bitwise JS RegExp JS Errors JS Scope JS Hoisting JS Strict Mode JS this Keyword JS Arrow Function JS Classes JS JSON JS Debugging JS Style Guide JS Best Practices JS Mistakes JS Performance JS Reserved Words

JS Versions

JS Versions JS 2009 (ES5) JS 2015 (ES6) JS 2016 JS 2017 JS 2018 JS IE / Edge JS History

JS Objects

Object Definitions Object Properties Object Methods Object Display Object Accessors Object Constructors Object Prototypes Object Reference Object Map() Object Set()

JS Functions

Function Definitions Function Parameters Function Invocation Function Call Function Apply Function Closures

JS Classes

Class Intro Class Inheritance Class Static

JS Async

JS Callbacks JS Asynchronous JS Promises JS Async/Await

JS HTML DOM

DOM Intro DOM Methods DOM Document DOM Elements DOM HTML DOM Forms DOM CSS DOM Animations DOM Events DOM Event Listener DOM Navigation DOM Nodes DOM Collections DOM Node Lists

JS Browser BOM

JS Window JS Screen JS Location JS History JS Navigator JS Popup Alert JS Timing JS Cookies

JS Web APIs

Web API Intro Web Forms API Web History API Web Storage API Web Worker API Web Fetch API Web Geolocation API

JS AJAX

AJAX Intro AJAX XMLHttp AJAX Request AJAX Response AJAX XML File AJAX PHP AJAX ASP AJAX Database AJAX Applications AJAX Examples

JS JSON

JSON Intro JSON Syntax JSON vs XML JSON Data Types JSON Parse JSON Stringify JSON Objects JSON Arrays JSON Server JSON PHP JSON HTML JSON JSONP

JS vs jQuery

jQuery Selectors jQuery HTML jQuery CSS jQuery DOM

JS Examples

JS Examples JS HTML DOM JS HTML Input JS HTML Objects JS HTML Events JS Browser JS Editor JS Exercises JS Quiz JS Certificate

JS References

JavaScript Objects HTML DOM Objects


JavaScript Set Objects

A Set is a collection of unique values.

Each value may occur only once in a Set.

A Set can hold any values of any data type.

How to Create a Set

Create a Set and add existing variables:

Example

// Create some variables
const a = "a";
const b = "b";
const c = "c";

// Create a Set
const letters = new Set();

// Add the values to the Set
letters.add(a);
letters.add(b);
letters.add(c);
Try it Yourself »

Create a Set and add literal values:

Example

// Create a Set
const letters = new Set();

// Add some values to the Set
letters.add("a");
letters.add("b");
letters.add("c");
Try it Yourself »

Pass an Array to the new Set() constructor:

Example

// Create a new Set
const letters = new Set(["a","b","c"]);
Try it Yourself »

For a Set, typeof returns object:

typeof letters;      // Returns object
Try it Yourself »

For a Set, instanceof Set returns true:

letters instanceof Set;  // Returns true
Try it Yourself »

Adding Elements to a Set

Example

letters.add("d");
letters.add("e");
Try it Yourself »

If you add equal elements, only the first will be saved:

Example

letters.add("a");
letters.add("b");
letters.add("c");
letters.add("c");
letters.add("c");
letters.add("c");
letters.add("c");
letters.add("c");
Try it Yourself »


Set Object Methods and Properties

new Set()Creates a new Set object
add()Adds a new element to the Set
clear()Removes all elements from a Set
delete()Removes an element specified by its value.
entries()Returns an array of the values in a Set object
has()Returns true if a value exists
forEach()Invokes a callback for each element
keys()Returns an array of the values in a Set object
values()Same as keys()
sizeReturns the element count