How can I save list of values in conversation object.

As of my understanding conversation is globally available in self script. Is there any other way of saving a variable and accessing it. How can we save a list of variables like an array in conversation object. I am doing the following but its not working;

function init() {

      var myArray = new Array();
     conversation.itemList = myArray;

}

function add_item() {
  var item = new Array();
  item[0] = 'first item';

 item[1] = 'second item' ;

conversation.itemList = item;

}

function show_items() {

  var items = conversation.itemList;

  return items.length(); // returns zero, There are no items in array?

}