完美解决了safari和微信浏览器的下拉回弹效果

JS代码varoverscroll=function(el){el.addEventListener('touchstart',function(){vartop=el.scrollTop,totalScroll=el.scrollHeight,currentScroll=top+el.offsetHeight;if(top===0){el.scrollTop=1;}elseif(currentScroll===totalScroll){el.scrollTop=top-1;}});el.addEventListener('touchmove',function(evt){if(el.offsetHeight