function overscroll(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.
// 参数为添加有overflow:scroll的dom元素
//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;
});
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();
}
});
}
