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:0padding:0font:12px/1.5 arialheight:2000px}
#jb51{width:100pxheight:200pxline-height:200px
text-align:centerborder:1p solid #ccc
background:#f5f5f5position:absoluteleft:-100pxtop:0}
#jb51_tit{position:absoluteright:-20pxtop:60px
width:20pxheight:60pxpadding:10px 0
background:#06ctext-align:center
line-height:18pxcolor:#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>
这是自己封装的原生js方法，为了偷懒，用了电jqurey。调用方法如下：
touchs._left(object)//往左滑动，
touchs._right(object)//往右滑动
touchs._top(object)//往上滑动
touchs._bottom(object)//往下滑动
说明：object的取值可以是一个id("#id")表达式，或者是一个样式表达式(".class"),或者标签的属性表达式("div[id=id]")等，只要可以用jqurey通过这个表达式获取到dom对象，这个表达式怎么写都可以。
