计算滚动条滚动的距离

方法一：
 var loadLock = false;
  function loadMore() {
	 if(jQuery('#bodyid').size() == 0)return ;

	  document.getElementById("bodyid").style.height=document.body.clientHeight;
	  var doe = document.documentElement || document.body,
		  scrollHeight = doe.scrollHeight, 
		  clientHeight = doe.clientHeight, 
		  scrollY = window.scrollY || doe.scrollTop,//滚动条滚动的距离
		  offset = scrollHeight - scrollY - clientHeight;
		  if(scrollY<=20&&scrollY>=0){
		  document.getElementById("topBtn").style.display="none";		
		} else if(scrollY>20&&offset<=100){
		  document.getElementById("topBtn").style.display="block";
		  document.getElementById("topBtn").style.cssText="bottom:100px;";
		}else if(scrollY>20&&offset>100){
		  document.getElementById("topBtn").style.display="block";
		  document.getElementById("topBtn").style.cssText="bottom:10px;";
		}
		  
  }
  window.onscroll = function() {
	  loadMore();
  };
方法二：
//回到页面顶部  
        $("#goTotop").click(function(){  
            $('body,html').animate({scrollTop:0},1500); //点击按钮让其回到页面顶部  
        });  
          
        $(window).scroll(function() {  
            var yheight1=window.pageYOffset; //滚动条距顶端的距离  
            var yheight=getScrollTop(); //滚动条距顶端的距离  
            var height =document.documentElement.clientHeight//浏览器可视化窗口的大小  
            var top=parseInt(yheight)+parseInt(height)-217;  
            var divobj=$(".kf");  
            divobj.attr('style','top:'+top+'px;');  
        })  
          
    /** 
     * 获取滚动条距离顶端的距离 
     * @return {}支持IE6 
     */  
    function getScrollTop() {  
            var scrollPos;  
            if (window.pageYOffset) {  
            scrollPos = window.pageYOffset; }  
            else if (document.compatMode && document.compatMode != 'BackCompat')  
            { scrollPos = document.documentElement.scrollTop; }  
            else if (document.body) { scrollPos = document.body.scrollTop; }   
            return scrollPos;   
    }