How to Add Elements to a JavaScript Array?

Here are different ways to add elements to an array in JavaScript.

1. Using push() Method

The push() method adds one or more elements to the end of an array and returns the new length of the array.

Syntax

array.push( element1, element2, . . ., elementN );

const arr = [10, 20, 30, 40];

arr.push(50);
console.log("Updated Array: ", arr);

arr.push(60, 70);
console.log("New Updated Array: ", arr);

Updated Array:  [ 10, 20, 30, 40, 50 ]
New Updated Array:  [
  10, 20, 30, 40,
  50, 60, 70
]

2. Using unshift() Method

The unshift() method adds one or more elements to the beginning of an array and returns the new length of the array.

Syntax

array.unshift( element1, element2, . . ., elementN );

const arr = [ 30, 40, 50 ];

arr.unshift(20);
console.log("Updated Array: ", arr);

arr.unshift(10, 5);
console.log("New Updated Array: ", arr);

Updated Array:  [ 20, 30, 40, 50 ]
New Updated Array:  [ 10, 5, 20, 30, 40, 50 ]

3. Using splice() Method

The splice() method changes the contents of an array by removing or replacing existing elements and/or adding new elements in place.

Syntax

array.splice( start_index, delete_count, item1, ..., itemN );

const arr = [ 10, 20, 30, 40, 50 ];

arr.splice(3, 0, 32, 35);
console.log("Updated Arrat: ", arr);

Updated Arrat:  [
  10, 20, 30, 32,
  35, 40, 50
]

4. Using concat() Method

The concat() method is used to merge two or more arrays. It does not change the existing arrays but returns a new array.

Syntax

let newArr = arr1.concat( arr2, arr3, . . ., arrN );

const arr1 = [ 10, 20, 30 ];
const arr2 = [ 40, 50 ];

const arr = arr1.concat(arr2);
console.log("Merged Array: ", arr);

Merged Array:  [ 10, 20, 30, 40, 50 ]

5. Using Spread Operator (...)

The spread operator can be used to add elements to an array. It returns a new array after addign some elements.

Syntax

let newArr = [ ...arr, element1, element2, . . ., elementN ];

const arr = [ 10, 20, 30, 40 ];
const newArr = [ ...arr, 50, 60 ];
console.log("Updated Array: ", newArr); 

Updated Array:  [ 10, 20, 30, 40, 50, 60 ]

6. Using Index Assignment

As we know the JavaScript arrays are dynamic in nature they do not have the finite length so we can assign a value to any index at any point of time. We can directly assign a value to a specific index to add an element to an array.

const arr = [ 10, 20, 30, 40 ];

arr[4] = 50;
console.log("Updated Array: ", arr);

Updated Array:  [ 10, 20, 30, 40, 50 ]