How to Declare an Array in JavaScript?

Array in JavaScript are used to store multiple values in a single variable. It can contain any type of data like - numbers, strings, booleans, objects, etc. There are varous ways to declare arrays in JavaScript, but the simplest and common is Array Litral Notations.

Using Array Literal Notation

The basic method to declare an array is using array litral notations. Use square bracket [] to declare an array and enclose comma-separated elements for initializing arrays.

Example: This example shows the different types of array declaration.

// Empty Array
const arr = [];
console.log(arr);

// Number Array
const numArr = [10, 20, 30, 40, 50];
console.log(numArr);

// String Array
const strArr = ["HTML", "CSS", "JS", "React"];
console.log(strArr);

// Multidimensional Array
const mat = [
    [0, 1],
    [2, 3],
];
console.log(mat);

[]
[ 10, 20, 30, 40, 50 ]
[ 'HTML', 'CSS', 'JS', 'React' ]
[ [ 0, 1 ], [ 2, 3 ] ]

Using Array() Constructor

Array constructor allows dynamically creating array and setting their initial state. It allows passing in elements as arguments to populate the array. If no argument is passed, an empty array is created.

Syntax

const arrayName = new Array(element0, element1, ..., elementN);

Example: Declaring an array using Array() constructor.

// Empty Array
const arr = new Array();
console.log(arr);

// Number Array
const numArr = new Array(10, 20, 30, 40, 50);
console.log(numArr);

// String Array
const strArr = new Array("HTML", "CSS", "JS", "React");
console.log(strArr);

// Multidimensional Array
const mat = new Array(Array(0, 1),Array(2, 3));
console.log(mat);

[]
[ 10, 20, 30, 40, 50 ]
[ 'HTML', 'CSS', 'JS', 'React' ]
[ [ 0, 1 ], [ 2, 3 ] ]

Using Array.of() Method

The Array.of() method creates a new Array with the specified elements. It is useful to ensure that single numeric argument is treated as elements rather than array lengths.

Example: Declare an array using Array.of() method.

// Empty Array
const arr = Array.of();
console.log(arr);

// Number Array
const numArr = Array.of(10, 20, 30, 40, 50);
console.log(numArr);

// String Array
const strArr = Array.of("HTML", "CSS", "JS", "React");
console.log(strArr);

// Multidimensional Array
const mat = Array.of(Array.of(0, 1), Array.of(2, 3));
console.log(mat);

[]
[ 10, 20, 30, 40, 50 ]
[ 'HTML', 'CSS', 'JS', 'React' ]
[ [ 0, 1 ], [ 2, 3 ] ]

Using Array.from() Method

The Array.from() method creates a new array from an array-like or iterable object. It allows for mapping functions to be applied to each element during the creation of the array.

Example 1: Converting a string to an array using Array.from() method.

let str = Array.from("Hello");
console.log(str);

[ 'H', 'e', 'l', 'l', 'o' ]