docs: function bindEvent() {
    var touch = {};
    var firstTouch;
  
    shortcut.addEventListener('touchstart', function (e) {
      var anchor = e.target.getAttribute('data-anchor');
  
      firstTouch = e.touches[0];
      touch.y1 = firstTouch.pageY;
      touch.anchor = anchor;
  
      scrollTo(anchor);
      
    });
  
    shortcut.addEventListener('touchmove', function (e) {
      firstTouch = e.touches[0];
      touch.y2 = firstTouch.pageY;
  
      var anchorHeight = 16;
  
      var delta = (touch.y2 - touch.y1) / anchorHeight | 0;
  
      var anchor = shortcutList[shortcutList.indexOf(touch.anchor) + delta];
  
      scrollTo(anchor);
  
      e.preventDefault();
      e.stopPropagation();
  
    });
  
    function scrollTo(anchor) {
      var maxScrollY = cityWrapper.clientHeight - cityScroller.clientHeight;
  
      var y = Math.min(0, Math.max(maxScrollY, anchorMap[anchor]));
  
      if (typeof y !== 'undefined') {
        scroll.scrollTo(0, y);
      }
    }
  }