jquery手机浮动导航

<div id="menu_fd" style="width:100%; z-index:1;"></div>

<div id="hiddenDiv" style="height:98px;overflow:hidden;display:none;">  </div>

var bar = $("#menu_fd"); var barTop = bar.offset().top; var hiddenDiv =$('#hiddenDiv');   $(window).scroll(function() { var scrollTop = $(this).scrollTop();if (scrollTop > barTop) {  hiddenDiv.css("display","block"); bar.css("position","fixed");    bar.animate({top:'0px'});} else { hiddenDiv.css("display","none");    bar.css("position","");    bar.css("top",""); }});