Get value from custom javascript

Hi all, if i have a custom javascript which is call a web service and return a string "HelloWord", how can i display the string to the form label control? thanks.

function fun() 
{
   var data="hello";   
   $.get("http://localhost/ws/service.asmx/HelloWord", function(response) {
            data = response;   
      }).error(function(){  
      alert("Sorry could not proceed");
      });    
   return data;
}