code: function () {
          if (req.status !== 200) {
            console.warn(req.responseText);
            return;
          }
          // Show the raw response text on page
          xmlOutput.textContent = req.responseText;
          // convert XML to javascript objects
          var json = sdmxmllib.mapSDMXMLResponse(req.responseText);
          // Convert to json and show on page
          jsonOutput.textContent = JSON.stringify(json, null, 2);
      }
docs: Response handler. Check the console for errors.