code: function requestJson(method, url, successCallback, failureCallback) {
      successCallback = successCallback || console.log;
      failureCallback = failureCallback || console.error || console.warn || console.log;
      var xhr = (typeof XDomainRequest !== 'undefined') ?
        (new XDomainRequest()) :
        (new XMLHttpRequest());
      xhr.onreadystatechange = function (event) {
        if (event.target.readyState === 4) {
          /* parse response as JSON */
          var responseJson;
          try { responseJson = window.JSON.parse(event.target.response); }
          catch (exception) { return failureCallback(event.target.response, exception); }
          /* perform callback according to HTTP status code */
          if (xhr.status > 0 && xhr.status < 400) {
            return successCallback(responseJson);
          } else {
            return failureCallback(responseJson);
          }
        }
      };
      xhr.open(method, url, true);
      xhr.send();
    }
docs: /* =================== /* Convenience Methods /* ===================