在HTML中的移动网页浏览器上下拉刷新

var PullToRefresh= function(callback, wrapper, instructionsText) {   //It creates dom elements and append them before content wrapper        // <div class="mainWrapper" style="overflow: scroll; height: 600px;">   <div class="pullToReloadWrapper"></div><div class = "contentWrapper"></div>   </div> is the markup.      // if main wrapper&#39;s height is > than content wrapper&#39;s   height, then change the main wrapper height to be the height of the content wrapper.      // scroll main wrapper.   // invoke initializeEvents() to inititalize the events};