docs: function (target, eventName, listener, useCapture) {
          var ver = System.utils.UserAgent.IE.getVersion();
          if (is(target, System.EventEmitter)) {
              target.on(eventName, listener, useCapture);
          } else if ((ver != -1 && ver <= 8) || is(target, Element)) {
              if (ver != -1 && ver < 11) {
                  target.attachEvent("on" + eventName, listener, useCapture);
              } else target.addEventListener(eventName, listener, useCapture);
          }
          return target;
      }