Updating Cookies With Jquery?

I'm trying to implement a side menu that saves it previous state (or selected item) after a submit or after the user refreshes the page.

I decided to use cookies to save the index of the selected item of the menu.

However, is not working everytime. What's going on?

Here's my code:

$(document).ready(function () {
var cookie = $.cookie("SelectedNode");
$('.t-link').click(function () {
var name = "SelectedNode";
var index = getIndex($(this));
$.cookie(name, null); //delete previous value
$.cookie(name, index);
alert("It should save: " + index + " but it saved: " + $.cookie("SelectedNode"));
});
});