Just starting to explore JQuery....

What I am trying to achieve is to compare previous value & selected
value of a drop down and then display a message. I am stuck as to how
I can retrieve previous value before the made the selection. Here is
what I got so far:

 jQuery(document).ready(
        jQuery("#status").change(function(){
            alert(" You are changing status to :" + this.value);
        });
    })