禁止微信浏览器的下拉滑动

解决思路：

1 先禁止body的滚动事件

2 再给需要scroll的元素加上自定义的滚动事件

注：加入此代码后要给需要scroll的元素加上.scroll的class

var overscroll = function (els) {        for (var i = 0; i < els.length; ++i) {            var el = els[i];            el.addEventListener('touchstart', function () {                var top = this.scrollTop                    , totalScroll = this.scrollHeight                    , currentScroll = top + this.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) {                    this.scrollTop = 1;                } else if (currentScroll === totalScroll) {                    this.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 (this.offsetHeight < this.scrollHeight)                    evt._isScroller = true;            });        }    };        //禁止body的滚动事件    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();        }    });        //给class为.scroll的元素加上自定义的滚动事件    overscroll(document.querySelectorAll('.scroll'));