Array.prototype.splice()

Overview.

The Array.prototype.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[, deleteCount[, item1[, item2[, ...]]]])

Parameters

start: Index at which to start changing the array (with origin 0). If greater than the length of the array, actual starting index will be set to the length of the array. If negative, will begin that many elements from the end of the array (-1 for the last element, -2 for the second to last element, and so on).
deleteCount (optional): An integer indicating the number of old array elements to remove. If deleteCount is 0, no elements are removed. If deleteCount is greater than the number of elements between start and the end of the array, all elements from start to the end of the array will be deleted.
item1, item2, ... (optional): The elements to add to the array, beginning at the start index. If you don't 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.

Examples

const months = ["Jan", "March", "April", "June"];
months.splice(1, 0, "Feb");
// months is now ["Jan", "Feb", "March", "April", "June"]

const months2 = ["Jan", "Feb", "March", "April", "June"];
months2.splice(4, 1);
// months2 is now ["Jan", "Feb", "March", "April"]

const months3 = ["Jan", "Feb", "March", "April"];
months3.splice(1, 2, "Feb-Apr");
// months3 is now ["Jan", "Feb-Apr", "April"]

const months = ['Jan', 'March', 'April', 'June'];

// Remove one element from the second index
months.splice(1, 1); // removes 'March'
// Result: ['Jan', 'April', 'June']

// Add an element at the third index
months.splice(2, 0, 'Feb');
// Result: ['Jan', 'April', 'Feb', 'June']

// Remove all elements after the second index
months.splice(2); 
// Result: ['Dec', 'April']