UrlLoaded プロパティ

// The client event UrlLoaded takes two parameters sender and e
// sender  is the object which is raising the event
// e is the TabItemEventArgs

function WebTab1_UrlLoaded(sender, e) {

         //Gets index of the tab involved in the event
         var tabIndex = e.get_tabIndex();

         //Assuming you have a label called labelOutput on the form
       var label = $get('labelOutput');

                 label.innerHTML = "Url loaded for tab with index '" + tabIndex + "'!";

             }