Javascript :: Add an item at any position in an array

It's easy, just use splice():

var myArray = [1, 2];
var valueToInsert = 1.5;
var indexToInsert = 1;
var deleteCount = 0;
myArray.splice(indexToInsert, deleteCount, valueToInsert);
console.log(JSON.stringify(myArray));

//outputs: [1, 1.5, 2]