Object Oriented After Page Load

Object Oriented After Page Load

I'm trying to write object oriented so :

$(function(){
      Obj.IntervalTime();
});

var Obj = {
    Features : {
        Length : $("#NAV").children().length
    },
    IntervalTime : function(){
        alert(Obj.Features.Length);
    },
};


<ul id = "NAV">
       <li>
             1
       </li>
       <li>
             2
       </li>
       <li>
             3
       </li>
 </ul>
code should alert 3 but alert 0
Why?

Thanks All