How to attach resize event to top window from iframe?

How to attach resize event to top window from iframe?

Hi Guys,

I would like to attach resize event to top window(main.html) when iframe(sub.html) ready.but seems it doesn't work,please see below code :

i dont know why it does not work,please,who could correct me ? or give me some suggestion on it? i will appreciate it.
  1. $(window.top.document).ready(function(){

          $(window.top).resize(function(){
            alert("grt!");
        })
        });