制止微信浏览器的下拉滑动

处理思绪：

1 先制止body的转动事宜

2 再给须要scroll的元素加上自定义的转动事宜

注：到场此代码后要给须要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;
            });
        }
    };
    
    //制止body的转动事宜
    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转动事宜
    overscroll(document.querySelectorAll('.scroll'));