javascript实现仿IE顶部的可关闭警告条_javascript技巧

function informationbar(){
this.displayfreq="always"
this.content=''
}
informationbar.prototype.setContent=function(data){
this.content=this.content+data
document.write(''+this.content+'')
}
informationbar.prototype.animatetoview=function(){
var barinstance=this
if (parseInt(this.barref.style.top)<0){
this.barref.style.top=parseInt(this.barref.style.top)+5+"px"
setTimeout(function(){barinstance.animatetoview()}, 50)
}
else{
if (document.all && !window.XMLHttpRequest)
this.barref.style.setExpression("top", 'document.compatMode=="CSS1Compat"? document.documentElement.scrollTop+"px" : body.scrollTop+"px"')
else
this.barref.style.top=0
}
}
informationbar.close=function(){
document.getElementById("informationbar").style.display="none"
if (this.displayfreq=="session")
document.cookie="infobarshown=1;path=/"
}
informationbar.prototype.setfrequency=function(type){
this.displayfreq=type
}
informationbar.prototype.initialize=function(){
if (this.displayfreq=="session" && document.cookie.indexOf("infobarshown")==-1 || this.displayfreq=="always"){
this.barref=document.getElementById("informationbar")
this.barheight=parseInt(this.barref.offsetHeight)
this.barref.style.top=this.barheight*(-1)+"px"
this.animatetoview()
}
}
window.onunload=function(){
this.barref=null
}