title: jQuery .offset() getting undefined for class `top` of var object
body: <p>I'm working on the following code, and a bit stumped why I'm getting an error in my debugger.  apparently in the line that starts with <code>var skillsLimit = ...</code> the class <code>.top</code> of var <code>skillsOffset</code> is undefined.   Am I setting the var for <code>skillsOffset</code> incorrectly here?</p>
  
  <pre><code>// Set Pie graph to position fixed during a specified range
          var $window = $(window);
          var windowHeight = $(window).height();
          var pos = $window.scrollTop(); //position of the scrollbar
          var $this = $(this);
  
          $window.bind('scroll', function(){ //when the user is scrolling...
              var pos = $window.scrollTop(); //position of the scrollbar              
              var skillsOffset = $('#skills').offset();
              var skillsLimit = $('#skills').skillsOffset.top + $('#skills').outerHeight();
              if ( pos &gt; skillsOffset ) {
                  $('.chartwell-pies').css({ 'position' : 'fixed' });
              }               
          });
  </code></pre>