docs: function () {
              var prevPageIndex,
                  currentPageIndex,
                  rowIndex,
                  row,
                  offset,
                  state = this.state,
                  pages = state.pages;
  
              prevPageIndex = util.bisectRight(pages, state.scrollTop, 'y0') - 1;
              if (prevPageIndex < 0) {
                  return 1;
              }
              offset = state.scrollTop + pages[prevPageIndex].height / 2;
              currentPageIndex = util.bisectRight(pages, offset, 'y0') - 1;
              rowIndex = pages[currentPageIndex].rowIndex;
              row = state.rows[rowIndex];
              return 1 + row[0];
  
          }