JQ滚动条效果

<script type="text/javascript" src="js/jquery-1.7.2.min.js"></script>




  <script type="text/javascript">
  $(function(){ //获取要定位元素距离浏览器顶部的距离
        var navH = $(".joinus_nav").offset().top;
   
   var show_detail_title_fixed = true;
   //滚动条事件
  $(window).scroll(function(){ //获取滚动条的滑动距离
  var scroH = $(this).scrollTop(); //滚动条的滑动距离大于等于定位元素距离浏览器顶部的距离，就固定，反之就不固定
  if(show_detail_title_fixed){
   if(scroH>=navH){
    $(".joinus_nav").css({"position":"fixed","top":"0","z-index":"99999",});
    $(".joinus_nav").show();
    }else if(scroH<navH){
     $(".joinus_nav").css({"position":"static"});
     
     }
     }
     });
     $("#close_detail_title_fixed").click(function(){
      show_detail_title_fixed = false;
      $(".detail_title_fixed").hide();
      });
      $("#go-backhome").click(function(){
       window.location.href="";
       });