how to add an item to a certain index in a javscript array code example

Example 1: 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());

Example 2: javascript add array to array at index

a1.splice(2, 0, ...a2);