try
                {
                    var response_obj = JSON.parse(xhttp.responseText);

                    console.log(response_obj);
                    callback(response_obj.hasOwnProperty("success") && response_obj.success && response_obj.hasOwnProperty("topd") && response_obj.topd);
                }
                catch(e)
                {
                    //no json string do nothing for now
                    console.log("error parsing json" + e);

                    callback(false);
                }