Find post back control with JavaScript

<script language="javascript" type="text/javascript">
         Sys.WebForms.PageRequestManager.getInstance().add_beginRequest(BeginRequestHandler);
         Sys.WebForms.PageRequestManager.getInstance().add_endRequest(EndRequestHandler);
         var PostBackCtrl;
         function BeginRequestHandler(sender, e) {
             PostBackCtrl = e.get_postBackElement();
         }

         function EndRequestHandler(sender, e) {

             if (PostBackCtrl.id.toLowerCase().indexOf("yourcontrolname") > 0 ) {
                 //This is your control which made post back
                 //write your code here
                 }
         }
     </script>