原理是利用瀏覽器cook來判斷,噹噹前頁面不存在cook時就是第一次開啟

程式碼: 

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引數錯誤");
        }
    }
    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讀取錯誤");
        return null;
    }
}

var ck=new Cookie("HasLoaded");  //每個頁面的new Cookie名HasLoaded不能相同
if(ck.Read()==null){//未載入過，Cookie內容為空
alert("首次開啟頁面");

    //設定儲存時間
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");  //設定Cookie。只要IE不關閉，Cookie就一直存在
}
else{//Cookie存在，表示頁面是被重新整理的
alert("頁面重新整理");
}