实现下拉刷新功能的JavaScript代码与优化

define(["js/main", "js/baseUtil", "js/constants"], function(main, baseUtil, constants) {
    var wrapper;
    var pullDownEl;
    var pullDownOffset;
    var pullUpEl;
    var pullUpOffset;
    var pageIndex = 1;
    var pageSize = 4;
    var util = {
        show : function() {
            var me = this;
            var bodyHeight = $("body").height();
            $("#wrapper").css("height", bodyHeight + "px");
            pullDownEl = document.getElementById('pullDown');
            pullDownOffset = pullDownEl.offsetHeight;
            wrapper = new iScroll('wrapper', {
                useTransition : true,
                topOffset : pullDownOffset,
                hideScrollbar : true,
                onRefresh : function() {
                    var pullDownEl = $("#pullDown")[0];
                    if (pullDownEl != null) {
                        if (pullDownEl.className.match('loading')) {
                            pullDownEl.className = '';
                            pullDownEl.querySelector('.pullDownLabel').innerHTML = '下拉以刷新...';
                            console.info('1');
                        }
                    }
                    var pullUpEl = $('#pullUp')[0];
                    if (pullUpEl != null) {

                        if (pullUpEl.className.match('loading')) {
                            pullUpEl.className = '';
                            pullUpEl.querySelector('.pullUpLabel').innerHTML = '下拉加载更多...';
                            console.info('2');
                        }
                    }
                },
                onScrollMove : function() {
                    var pullDownEl = $("#pullDown")[0];
                    if (pullDownEl != null) {
                        var pullDownOffset = pullDownEl.offsetHeight;
                        if (this.y > 5 && !pullDownEl.className.match('flip')) {
                            pullDownEl.className = 'flip';
                            pullDownEl.querySelector('.pullDownLabel').innerHTML = '释放以刷新...';
                            this.minScrollY = 0;
                            console.info('3');
                        } else if (this.y < 5 && pullDownEl.className.match('flip')) {
                            pullDownEl.className = '';
                            pullDownEl.querySelector('.pullDownLabel').innerHTML = '下拉以刷新...';
                            this.minScrollY = -pullDownOffset;
                            console.info('4');
                        }
                    }
                    var pullUpEl = $('#pullUp')[0];
                    if (pullUpEl != null) {
                        var pullUpOffset = pullUpEl.offsetHeight;
                        if (this.y < (this.maxScrollY - 5) && !pullUpEl.className.match('flip')) {
                            pullUpEl.className = 'flip';
                            pullUpEl.querySelector('.pullUpLabel').innerHTML = '释放后加载更多...';
                            this.maxScrollY = this.maxScrollY;