js侧边固定悬浮浮动效果

效果是 ：滚动条滚动到一定程度后左侧栏才会触发开始随着浮动，左侧能滚动的范围也就是右侧高度，如：

//内页侧边栏固定悬浮
 function side_absolute(left,right,wrap){
   var about_l_height=left.outerHeight(true);
   var about_con=right.outerHeight(true);

   function run(){
    if( about_con>about_l_height ){ //右侧的内容高度比左侧导航高时才触发
      if( (($(window).scrollTop()-150)+about_l_height)>=about_con && $(window).height()>about_l_height){ //判断是否到容器底部了
        left.css({position:'relative',left:'0px',top:about_con-about_l_height});
      }else if($(window).scrollTop()>=150 && $(window).height()>about_l_height && about_con>about_l_height){
        right.addClass('float_r');
        wrap.css({position:'relative'});
        left.css({position:'fixed',left:wrap.offset().left,top:0});
      }else if( $(window).scrollTop()<150 ) {
        left.css({position:'static',left:'0px'});
      }else if($(window).height()<about_l_height){
        left.css({position:'static',left:'0px'});
      }
    }
   }


  $(window).scroll(function(){
    run()
  });


  $(window).resize(function(){
    run()
  });

  if( left.css('position')=='fixed' ){
    $(window).resize(function(){
      left.css({left:wrap.offset().left});
    });
  }else{
    left.css({left:'0px'});
  }

 }

 side_absolute($('.about_l'),$('.about_l').next(),$('#about_div'));

 $(window).resize(function(){
   side_absolute($('.about_l'),$('.about_l').next(),$('#about_div'));
 });

js

效果：https://www.honhe.com/intros/intro.jhtml