js Cookie 判断页面是否为第一次打开

JScript code：
function Cookie(key,value)
{
    this.key=key;
    if(value!=null)
    {
        this.value=escape(value);
    }
    this.expiresTime=null;
    this.domain=null;
    this.path="/";
    this.secure=null;
}
Cookie.prototype.setValue=function(value){this.value=escape(value);}
Cookie.prototype.getValue=function(){return (this.value);}

Cookie.prototype.setExpiresTime=function(time){this.expiresTime=time;}
Cookie.prototype.getExpiresTime=function(){return this.expiresTime;}

Cookie.prototype.setDomain=function(domain){this.domain=domain;}
Cookie.prototype.getDomain=function(){return this.domain;}

Cookie.prototype.setPath=function(path){this.path=path;}
Cookie.prototype.getPath=function(){return this.path;}

Cookie.prototype.Write=function(v)
{
    if(v!=null)
    {
        this.setValue(v);
    }
    var ck=this.key+"="+this.value;
    if(this.expiresTime!=null)
    {
        try
        {
            ck+=";expires="+this.expiresTime.toUTCString();;
        }
        catch(err)
        {
            alert("expiresTime参数错误");
        }
    }
    if(this.domain!=null)
    {
        ck+=";domain="+this.domain;
    }
    if(this.path!=null)
    {
        ck+=";path="+this.path;
    }
    if(this.secure!=null)
    {
        ck+=";secure";
    }
    document.cookie=ck;
}
Cookie.prototype.Read=function()
{
    try
    {
        var cks=document.cookie.split("; ");
        var i=0;
        for(i=0;i <cks.length;i++)
        {
            var ck=cks[i];
            var fields=ck.split("=");
            if(fields[0]==this.key)
            {
                this.value=fields[1];
                return (this.value);
            }
        }
        return null;
    }
    catch(err)
    {
        alert("cookie读取错误");
        return null;
    }
}

HTML code：
<script type="text/javascript" src="Cookie.js"></script>
<script type="text/javascript" language="javascript">
 window.onload=function(){
  var ck=new Cookie("HasLoaded");  //每个页面的new Cookie名HasLoaded不能相同
  if(ck.Read()==null){//未加载过，Cookie内容为空
      alert("首次打开页面");
    
     //设置保存时间
     var dd = new Date();
     dd = new Date(dd.getYear() + 1900, dd.getMonth(), dd.getDate());
     dd.setDate(dd.getDate() + 365);
     ck.setExpiresTime(dd);

      ck.Write("true");  //设置Cookie。只要IE不关闭，Cookie就一直存在
  }
  else{//Cookie存在，表示页面是被刷新的
   alert("页面刷新");
  }
 }
</script>