js实现分享到随页面滚动而滑动效果的方法

本文实例讲述了js实现分享到随页面滚动而滑动效果的方法。分享给大家供大家参考。具体如下：

页面向上向下滚动，分享到的模块随着滑动。

要点：

代码如下:

var scrtop =document.documentElement.scrollTop||document.body.scrollTop;
var height = document.documentElement.clientHeight||document.body.clientHeight;
var top = scrtop + (height - jb51.offsetHeight)/2;
top = parseInt(top);

获得页面垂直居中的位置
 
上代码：

<!DOCTYPE html>
<html>
<head>
<meta charset="gb2312" />
<title>无标题文档</title>
<style>
body{margin:0; padding:0; font:12px/1.5 arial; height:2000px;}
#jb51{width:100px; height:200px; line-height:200px;
text-align:center; border:1p solid #ccc;
background:#f5f5f5; position:absolute; left:-100px; top:0;}
#jb51_tit{position:absolute; right:-20px; top:60px;
width:20px; height:60px; padding:10px 0;
background:#06c; text-align:center;
line-height:18px; color:#fff;}
</style>
<script>
window.onload = function(){
 var jb51 = document.getElementById("jb51");
 jb51.onmouseover = function(){
 startrun(jb51,0,"left")
 }
 jb51.onmouseout = function(){
 startrun(jb51,-100,"left")
 }
 window.onscroll = window.onresize = function(){
 var scrtop=document.documentElement.scrollTop||document.body.scrollTop;
 var height=document.documentElement.clientHeight||document.body.clientHeight;
 var top = scrtop + (height - jb51.offsetHeight)/2;
 top = parseInt(top);
 startrun(jb51,top,"top")
 }
}
var timer = null
function startrun(obj,target,direction){
 clearInterval(timer);
 timer = setInterval(function(){
 var speed = 0;
 if(direction == "left"){
  speed = (target-obj.offsetLeft)/8;
  speed = speed>0?Math.ceil(speed):Math.floor(speed);
  if(obj.offsetLeft == target){
  clearInterval(timer);
  }else{
  obj.style.left = obj.offsetLeft + speed + "px";
  }
 }
  if(direction == "top"){
  speed = (target-obj.offsetTop)/8;
  speed = speed>0?Math.ceil(speed):Math.floor(speed);
  if(obj.offsetTop == target){
  clearInterval(timer);
  }else{
  obj.style.top = obj.offsetTop + speed + "px";
  }
  document.title = obj.offsetTop + ',' + target + ',' +speed;
 }
 },30)
}
</script>
</head>
<body>
<div id="jb51">
 分享到内容
 <span id="jb51_tit">分享到</span>
</div>
</body>
</html>

希望本文所述对大家的javascript程序设计有所帮助。