jquery touch 移动端上下滑动加载

var touchStart, touchEnd, touchDiff = 80;

        $(window).on({

            'touchstart': function (e) {

                touchStart = e.originalEvent.changedTouches[0].clientY;

            },

            'touchend': function (e) {

                touchEnd = e.originalEvent.changedTouches[0].clientY;

                var diff = touchStart - touchEnd;

                if (diff >= touchDiff) { // direction down

                    if ($(window).scrollTop() + $(window).height() >= $(document).height()) { // scroll bottom

                        buildList(pageIndex + 1);

                    }

                } else if (diff <= -touchDiff) { // direction up

                    if ($(window).scrollTop() == 0) { // scroll top

                        buildList(1);

                    }

                }

            }

        });