code: function keydownHook(event) {
          var keyHandled = false;
  
          switch (event.keyCode) {
          case KeyEvent.DOM_VK_UP:
              selectNextItem(-1);
              keyHandled = true;
              break;
          case KeyEvent.DOM_VK_DOWN:
              selectNextItem(+1);
              keyHandled = true;
              break;
          case KeyEvent.DOM_VK_ENTER:
          case KeyEvent.DOM_VK_RETURN:
              if ($dropdownItem) {
                  $dropdownItem.trigger("click");
              }
              keyHandled = true;
              break;
          case KeyEvent.DOM_VK_BACK_SPACE:
          case KeyEvent.DOM_VK_DELETE:
              if ($dropdownItem) {
                  removeSelectedItem(event);
                  keyHandled = true;
              }
              break;
          }
  
          if (keyHandled) {
              event.stopImmediatePropagation();
              event.preventDefault();
          }
          return keyHandled;
      }
docs: Handles the Key Down events
  @param {KeyboardEvent} event
  @return {boolean} True if the key was handled