Mobile的HTML5网页内快速滚动和回弹的效果

var overscroll = function(el) {
  el.addEventListener(‘touchstart‘, function() {
    var top = el.scrollTop
      , totalScroll = el.scrollHeight
      , currentScroll = top + el.offsetHeight;
    //If we‘re at the top or the bottom of the containers
    //scroll, push up or down one pixel.
    //
    //this prevents the scroll from "passing through" to
    //the body.
    if(top === 0) {
      el.scrollTop = 1;
    } else if(currentScroll === totalScroll) {
      el.scrollTop = top - 1;
    }
  });
  el.addEventListener(‘touchmove‘, function(evt) {
    //if the content is actually scrollable, i.e. the content is long enough
    //that scrolling can occur
    if(el.offsetHeight < el.scrollHeight)
      evt._isScroller = true;
  });
}
overscroll(document.querySelector(‘.scroll‘));
document.body.addEventListener(‘touchmove‘, function(evt) {
  //In this case, the default behavior is scrolling the body, which
  //would result in an overflow.  Since we don‘t want that, we preventDefault.
  if(!evt._isScroller) {
    evt.preventDefault();
  }
});