title: JQuery Drag & Drop How to swap already dragged with newly dragged item
body: <p>I have a set of divs that can be dragged on another set of div's. Hear is the code</p>
  
  <pre><code>    $('#mapColumns div').draggable({
            containment: '#content',
            cursor: 'move',
            revert: 'invalid',
            stack:'#mapRow div'
      });
      alert($('#mapRow div'));
  
      $('#mapRow div').droppable({
          accept: '#mapColumns div',
          drop: handleColumnDrop
      });
  </code></pre>
  
  <p>What I want to do is if a div is dragged on a droppable div which already has a previously dragged div placed on it then I want to revert the previously  dragged div to its original position and the newly dragged to take its place. How do I achieve this.</p>
  
  <p>The problem is I am not able to get handle on div which is already dragged on droppable element</p>
  
  <p>Please Help.</p>