css scroll bug

滚动区域不能设置overflow

　　　　var doc = $(document),
            win = $(window),

            h = $("#head"),
            b = $("#body"),
            f = $("#foot"),
            itemList = $("#itemList"),
            loadDom = $("#loadDom"),

            loading = false;
         win.scroll(function(){

            var flag = (doc.height()) <= (window.innerHeight + win.scrollTop())

               if(!loading && flag) {
                loading =true;
                loadDom.removeClass("hidden");
                setTimeout(function(){
                     itemList.append(loadTpl("#tpl-item"));
                    loading =false;
                },3000);
            }
        });