code: function (event) {
                      this._lastKeyOrBlurEvent = this._currentKeyOrBlurEvent;
                      switch (event.type) {
                          case "keyup":
                              if (event.keyCode === Key.shift) {
                                  this._currentKeyOrBlurEvent = null;
                              } else {
                                  this._currentKeyOrBlurEvent = "keyboard";
                              }
                              break;
                          case "focusout":
                              //anchor element no longer in focus, clear up the stack
                              this._currentKeyOrBlurEvent = null;
                              break;
                          default:
                              break;
  
                      }
                  }
docs: Support for keyboard navigation