how to assign value to particular index in arry in js code example

Example 1: javascript push in specific index

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

Example 2: javascript Inserting values in between an array

myArray.splice(index, itemsToDelete, item1ToAdd, item2ToAdd, ...)