code: function (state) {
          if (isObject(state)) {
              var current = state.before;
              delete state.before;
              this.fireEvent('pageChange',{
                  type      : 'pageChange',
                  prevValue : state.page,
                  newValue  : current.page,
                  prevState : state,
                  newState  : current
              });
          }
      }
docs: Fires a pageChange event in the form of a standard attribute change
  event with additional properties prevState and newState.
  @method _firePageChange
  @param state {Object} the result of getState(oldState)
  @protected