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 Iterables JS Sets JS Maps 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 Iterables Object Sets Object Maps Object Reference

JS Functions

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

JS Classes

Class Intro Class Inheritance Class Static

JS Async

JS Callbacks JS Asynchronous JS Promises JS Async/Await


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


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


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



JS vs jQuery

jQuery Selectors jQuery HTML jQuery CSS jQuery DOM

JS Graphics

JS Graphics JS Canvas JS Plotly JS Chart.js JS Google Chart JS D3.js

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. W3Schools in English. Lessons for beginners


JavaScript Arrays

An array is a special variable, which can hold more than one value:

const cars = ["Saab", "Volvo", "BMW"];
Try it Yourself »

Why Use Arrays?

If you have a list of items (a list of car names, for example), storing the cars in single variables could look like this:

let car1 = "Saab";
let car2 = "Volvo";
let car3 = "BMW";

However, what if you want to loop through the cars and find a specific one? And what if you had not 3 cars, but 300?

The solution is an array!

An array can hold many values under a single name, and you can access the values by referring to an index number.

Creating an Array

Using an array literal is the easiest way to create a JavaScript Array.


const array_name = [item1, item2, ...];      

It is a common practice to declare arrays with the const keyword.

Learn more about const with arrays in the chapter: JS Array Const.


const cars = ["Saab", "Volvo", "BMW"];
Try it Yourself »

Spaces and line breaks are not important. A declaration can span multiple lines:


const cars = [
Try it Yourself »

You can also create an array, and then provide the elements:


const cars = [];
cars[0]= "Saab";
cars[1]= "Volvo";
cars[2]= "BMW";
Try it Yourself »

Using the JavaScript Keyword new

The following example also creates an Array, and assigns values to it:


const cars = new Array("Saab", "Volvo", "BMW");
Try it Yourself »

The two examples above do exactly the same.

There is no need to use new Array().

For simplicity, readability and execution speed, use the array literal method.

Accessing Array Elements

You access an array element by referring to the index number:

const cars = ["Saab", "Volvo", "BMW"];
let car = cars[0];
Try it Yourself »

Note: Array indexes start with 0.

[0] is the first element. [1] is the second element.

Changing an Array Element

This statement changes the value of the first element in cars:

cars[0] = "Opel";


const cars = ["Saab", "Volvo", "BMW"];
cars[0] = "Opel";
Try it Yourself »

Access the Full Array

With JavaScript, the full array can be accessed by referring to the array name:


const cars = ["Saab", "Volvo", "BMW"];
document.getElementById("demo").innerHTML = cars;
Try it Yourself »

Arrays are Objects

Arrays are a special type of objects. The typeof operator in JavaScript returns "object" for arrays.

But, JavaScript arrays are best described as arrays.

Arrays use numbers to access its "elements". In this example, person[0] returns John:


const person = ["John", "Doe", 46];
Try it Yourself »

Objects use names to access its "members". In this example, person.firstName returns John:


const person = {firstName:"John", lastName:"Doe", age:46};
Try it Yourself »

Array Elements Can Be Objects

JavaScript variables can be objects. Arrays are special kinds of objects.

Because of this, you can have variables of different types in the same Array.

You can have objects in an Array. You can have functions in an Array. You can have arrays in an Array:

myArray[0] =;
myArray[1] = myFunction;
myArray[2] = myCars;

Array Properties and Methods

The real strength of JavaScript arrays are the built-in array properties and methods:

cars.length   // Returns the number of elements
cars.sort()   // Sorts the array

Array methods are covered in the next chapters.

The length Property

The length property of an array returns the length of an array (the number of array elements).


const fruits = ["Banana", "Orange", "Apple", "Mango"];
let length = fruits.length;
Try it Yourself »

The length property is always one more than the highest array index.

Accessing the First Array Element


const fruits = ["Banana", "Orange", "Apple", "Mango"];
let fruit = fruits[0];
Try it Yourself »

Accessing the Last Array Element


const fruits = ["Banana", "Orange", "Apple", "Mango"];
let fruit = fruits[fruits.length - 1];
Try it Yourself »

Looping Array Elements

One way to loop through an array, is using a for loop:


const fruits = ["Banana", "Orange", "Apple", "Mango"];
let fLen = fruits.length;

let text = "<ul>";
for (let i = 0; i < fLen; i++) {
  text += "<li>" + fruits[i] + "</li>";
text += "</ul>";
Try it Yourself »

You can also use the Array.forEach() function:


const fruits = ["Banana", "Orange", "Apple", "Mango"];

let text = "<ul>";
text += "</ul>";

function myFunction(value) {
  text += "<li>" + value + "</li>";
Try it Yourself »

Adding Array Elements

The easiest way to add a new element to an array is using the push() method:


const fruits = ["Banana", "Orange", "Apple"];
fruits.push("Lemon");  // Adds a new element (Lemon) to fruits
Try it Yourself »

New element can also be added to an array using the length property:


const fruits = ["Banana", "Orange", "Apple"];
fruits[fruits.length] = "Lemon";  // Adds "Lemon" to fruits
Try it Yourself »


Adding elements with high indexes can create undefined "holes" in an array:


const fruits = ["Banana", "Orange", "Apple"];
fruits[6] = "Lemon";  // Creates undefined "holes" in fruits
Try it Yourself »

Associative Arrays

Many programming languages support arrays with named indexes.

Arrays with named indexes are called associative arrays (or hashes).

JavaScript does not support arrays with named indexes.

In JavaScript, arrays always use numbered indexes.  


const person = [];
person[0] = "John";
person[1] = "Doe";
person[2] = 46;
person.length;    // Will return 3
person[0];        // Will return "John"
Try it Yourself »

If you use named indexes, JavaScript will redefine the array to an object.

After that, some array methods and properties will produce incorrect results.


const person = [];
person["firstName"] = "John";
person["lastName"] = "Doe";
person["age"] = 46;
person.length;     // Will return 0
person[0];         // Will return undefined
Try it Yourself »

The Difference Between Arrays and Objects

In JavaScript, arrays use numbered indexes.  

In JavaScript, objects use named indexes.

Arrays are a special kind of objects, with numbered indexes.

When to Use Arrays. When to use Objects.

  • JavaScript does not support associative arrays.
  • You should use objects when you want the element names to be strings (text).
  • You should use arrays when you want the element names to be numbers.

JavaScript new Array()

JavaScript has a built-in array constructor new Array().

But you can safely use [] instead.

These two different statements both create a new empty array named points:

const points = new Array();
const points = [];

These two different statements both create a new array containing 6 numbers:

const points = new Array(40, 100, 1, 5, 25, 10);
const points = [40, 100, 1, 5, 25, 10];
Try it Yourself »

The new keyword can produce some unexpected results:

// Create an array with three elements:
const points = new Array(40, 100, 1);
Try it Yourself »
// Create an array with two elements:
const points = new Array(40, 100);
Try it Yourself »
// Create an array with one element ???
const points = new Array(40);  
Try it Yourself »

A Common Error

const points = [40];

is not the same as:

const points = new Array(40);
// Create an array with one element:
const points = [40];
Try it Yourself »
// Create an array with 40 undefined elements:
const points = new Array(40);  
Try it Yourself »

How to Recognize an Array

A common question is: How do I know if a variable is an array?

The problem is that the JavaScript operator typeof returns "object":

const fruits = ["Banana", "Orange", "Apple"];
let type = typeof fruits;
Try it Yourself »

The typeof operator returns object because a JavaScript array is an object.

Solution 1:

To solve this problem ECMAScript 5 (JavaScript 2009) defined a new method Array.isArray():

Try it Yourself »

Solution 2:

The instanceof operator returns true if an object is created by a given constructor:

const fruits = ["Banana", "Orange", "Apple"];

fruits instanceof Array;
Try it Yourself »

Complete Array Reference

For a complete Array reference, go to our:

Complete JavaScript Array Reference.

The reference contains descriptions and examples of all Array properties and methods.

Test Yourself With Exercises


Get the value "Volvo" from the cars array.

const cars = ["Saab", "Volvo", "BMW"];
let x = ;