how to add a new entry in specific position and push the others to following numbers 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: insert into array js

// for me lol... pls don't delete!
// use splice to insert element
// arr.splice(index, numItemsToDelete, item); 
var list = ["hello", "world"]; 
list.splice( 1, 0, "bye"); 
//result
["hello", "bye", "world"]