iscroll.js的上拉下拉刷新时无法回弹的解决方法

 myScroll = new iScroll('wrapper', {
  vScrollbar: false,
  useTransition: true,
  topOffset: pullDownOffset,
  onRefresh: function () {
   if (pullDownEl.className.match('loading')) {
    pullDownEl.className = '';
    pullDownEl.querySelector('.pullDownLabel').innerHTML = 'Pull down to refresh...';
   } else if (pullUpEl.className.match('loading')) {
    pullUpEl.className = '';
    pullUpEl.querySelector('.pullUpLabel').innerHTML = 'Pull up to load more...';
   }
  },
  onScrollMove: function () {
   if (this.y > 5 && !pullDownEl.className.match('flip')) {
    pullDownEl.className = 'flip';
    pullDownEl.querySelector('.pullDownLabel').innerHTML = 'Release to refresh...';
    this.minScrollY = 0;
   } else if (this.y < 5 && pullDownEl.className.match('flip')) {
    pullDownEl.className = '';
    pullDownEl.querySelector('.pullDownLabel').innerHTML = 'Pull down to refresh...';
    this.minScrollY = -pullDownOffset;
   } else if (this.y < (this.maxScrollY - 5) && !pullUpEl.className.match('flip')) {
    pullUpEl.className = 'flip';
    pullUpEl.querySelector('.pullUpLabel').innerHTML = 'Release to refresh...';
    this.maxScrollY = this.maxScrollY;
   } else if (this.y > (this.maxScrollY + 5) && pullUpEl.className.match('flip')) {
    pullUpEl.className = '';
    pullUpEl.querySelector('.pullUpLabel').innerHTML = 'Pull up to load more...';
    this.maxScrollY = pullUpOffset;
   }
  },
  onScrollEnd: function () {
   if (pullDownEl.className.match('flip')) {
    pullDownEl.className = 'loading';
    pullDownEl.querySelector('.pullDownLabel').innerHTML = 'Loading...';
    pullDownAction();
   } else if (pullUpEl.className.match('flip')) {
    pullUpEl.className = 'loading';
    pullUpEl.querySelector('.pullUpLabel').innerHTML = 'Loading...';
    pullUpAction();
   }
  }
 });

  onScrollMove: function () {
   if((this.y < this.maxScrollY) && (this.pointY < 1)){
    this.scrollTo(0, this.maxScrollY, 400);
    return;
   } else if (this.y > 0 && (this.pointY > window.innerHeight - 1)) {
    this.scrollTo(0, 0, 400);
    return;
   }

   ......
  }