JavaScript Array Splice

March 11, 2020

JavaScript Array Splice

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

const months = ['Jan', 'March', 'April', 'June'];
months.splice(1, 0, 'Feb');
// inserts at index 1
// expected output: Array ["Jan", "Feb", "March", "April", "June"]

months.splice(4, 1, 'May');
// replaces 1 element at index 4
// expected output: Array ["Jan", "Feb", "March", "April", "May"]

let arrDeletedItems = array.splice(start[, deleteCount[, item1[, item2, ...]]])

The index at which to start changing the array.

deleteCount Optional
An integer indicating the number of elements in the array to remove from start.

item1, item2, ... Optional
The elements to add to the array, beginning from start. If you do not specify any elements, splice() will only remove elements from the array.

Return value

An array containing the deleted elements.
If only one element is removed, an array of one element is returned.
If no elements are removed, an empty array is returned.


Remove 0 (zero) elements before index 2, and insert "drum"

let myFish = ['angel', 'clown', 'mandarin', 'sturgeon']
let removed = myFish.splice(2, 0, 'drum')

// myFish is ["angel", "clown", "drum", "mandarin", "sturgeon"] 
// removed is [], no elements removed

Remove 1 element at index 3

let myFish = ['angel', 'clown', 'drum', 'mandarin', 'sturgeon']
let removed = myFish.splice(3, 1)

// removed is ["mandarin"]
// myFish is ["angel", "clown", "drum", "sturgeon"] 

Remove all elements after index 2 (incl.)

let myFish = ['angel', 'clown', 'mandarin', 'sturgeon']
let removed = myFish.splice(2)

// myFish is ["angel", "clown"]
// removed is ["mandarin", "sturgeon"]