A simple test,
$.ajax({
     url: "http://localhost:45166/userAdmin/UserAccountInfo/?child=true&json=true",
     dataType: 'jsonp',
     success: function(json) {

         //jsonp return a javascript
         // callback({json:value})
     },
     error: function() {

     },
 });

in the Controller

return a javascript as ActionResult:
return JavaScript("alert({'TEST'})");
the javascript can be run in the client site.