How to initialize an array in JavaScript ?
Initializing an array in JavaScript involves creating a variable and assigning it an array literal, which consists of square brackets enclosing optional comma-separated elements. These elements can be of any data type or can be omitted for an empty array.
To initialize an array in JavaScript we can use methods given below:
Table of Content
- Using an array as literal
- Using an array as an object/Array() constructor
Using an array as literal
Initializing an array using the array literal approach involves directly assigning square brackets [] to a variable. This creates an empty array or populates it with elements enclosed within the brackets, offering a concise and straightforward method for array initialization in JavaScript.
Example: Below is an example of array as literal.
const sports = ["cricket", "football",
"competitive-programming"];
console.log('sports=', sports);
const myArray = [];
console.log('myArray=', myArray);
const score = [420, 10, 1, 12, 102];
console.log('score=', score);
Output
sports= [ 'cricket', 'football', 'competitive-programming' ] myArray= [] score= [ 420, 10, 1, 12, 102 ]
Example 2: The line breaks and new lines do not impact arrays, they store in their normal way.
const sports = ["cricket",
"football",
"competitive-programming"];
console.log('sports=', sports);
const myArray = [];
console.log('myArray=', myArray);
const score = [420, 10, 1,
12, 102];
console.log('score=', score);
Output
sports= [ 'cricket', 'football', 'competitive-programming' ] myArray= [] score= [ 420, 10, 1, 12, 102 ]
Using an array as an object/Array() constructor
Initializing an array using the Array constructor involves invoking new Array() and optionally passing initial elements as arguments. Alternatively, specifying the desired length as a single argument creates an array with undefined elements, offering flexibility in array initialization in JavaScript.
Example: Below is an example of array as an object.
const sports = new Array("cricket", "football", "competitive-programming");
console.log('sports=', sports);
const myArray = new Array();
console.log('myArray=', myArray);
const points = new Array();
console.log('points=', points);
const score = new Array(140, 200, 21, 53, 245, 20);
console.log('score=', score);
Output
sports= [ 'cricket', 'football', 'competitive-programming' ] myArray= [] points= [] score= [ 140, 200, 21, 53, 245, 20 ]
The Difference Between Array() and []
In JavaScript, Array() and [] are two ways to create arrays, but there is a subtle difference between them.
| Feature | Array() Constructor | Array Literal ([]) |
|---|---|---|
| Type of Creation | Built-in constructor function for creating arrays. | Shorthand notation for creating arrays. |
Call with new Keyword | Can be called with or without the new keyword. | Not applicable, as it is a shorthand notation, not a function. |
| Object Creation | When called with new, it creates a new array object. | Not applicable, as it doesn’t involve explicit object creation. |
| Return Type | Returns an array object. | Returns a newly created array. |
| Arguments | Can take arguments to specify initial elements of the array. | Can be used to create empty arrays or initialize with elements. |
| Example | javascript const array1 = new Array(1, 2, 3);// Using constructor with newconst array2 = Array(4, 5, 6); // Using constructor without new | javascript const array3 = [7, 8, 9]; // Creating an array using literal notation const emptyArray = []; // Creating an empty array |
When using Array() with the new keyword, it creates a new array object. When using [] (array literal notation), it also creates a new array object. However, if Array() is called without new and without arguments, it returns an empty array, while [] always creates a new empty array.
Example:
const newArray = Array(); // Returns an empty array
const literalArray = []; // Creates a new empty array