JAVASCRIPT

javascript push in specific index

arr.splice(index, 0, item);
//explanation:
inserts "item" at the specified "index",
deleting 0 other items before it

insert item into array specific index javascript

myArray.splice(index, 0, item);

Add an element to an array at a specific index with JavaScript

const sidebarMenu = ['home', 'about', 'contact'];
sidebarMenu.splice(2, 0, 'courses'); //Add Single Element
sidebarMenu.splice(2, 0, 'courses', 'profile'); //Add Multiple Elements

How to insert an item into an array at a specific index JavaScript

var arr = [];
arr[0] = "Jani";
arr[1] = "Hege";
arr[2] = "Stale";
arr[3] = "Kai Jim";
arr[4] = "Borge";

console.log(arr.join());
arr.splice(2, 0, "Lene");
console.log(arr.join());

insert element in specific index javascript

const numbers = ['one', 'two', 'four', 'five']
numbers.splice(2, 0, 'three'); // one,two,three,four,five

javascript add item by index

// Be careful!

const arr = [ 1, 2, 3, 4 ];
arr[5] = 'Hello, world!';

console.log(arr); // [ 1, 2, 3, 4, <1 empty item>, 'Hello, world!' ]
console.log(arr.length); // 6