code: function ()
      {
          var node = null;
          if (this.xhr.responseXML && this.xhr.responseXML.documentElement) {
              node = this.xhr.responseXML.documentElement;
              if (node.tagName == "parsererror") {
                  Strophe.error("invalid response received");
                  Strophe.error("responseText: " + this.xhr.responseText);
                  Strophe.error("responseXML: " +
                                Strophe.serialize(this.xhr.responseXML));
                  throw "parsererror";
              }
          } else if (this.xhr.responseText) {
              Strophe.error("invalid response received");
              Strophe.error("responseText: " + this.xhr.responseText);
              Strophe.error("responseXML: " +
                            Strophe.serialize(this.xhr.responseXML));
          }
  
          return node;
      }
docs: PrivateFunction: getResponse
  Get a response from the underlying XMLHttpRequest.
  
  This function attempts to get a response from the request and checks
  for errors.
  
  Throws:
  "parsererror" - A parser error occured.
  
  Returns:
  The DOM element tree of the response.