//寫cookies
function setCookie(name,value){
    var Days = 30;
    var exp = new Date();
    exp.setTime(exp.getTime() + Days*24*60*60*1000);
    document.cookie = name + "="+ escape (value) + ";expires=" + exp.toGMTString();
}
//讀cookie
function getCookie(name){
    var arr,reg=new RegExp("(^| )"+name+"=([^;]*)(;|$)");
    if(arr=document.cookie.match(reg))
        return unescape(arr[2]);
    else
        return null;
}
//刪除cookie
function delCookie(name){
    var exp = new Date();
    exp.setTime(exp.getTime() - 1);
    var cval=getCookie(name);
    if(cval!=null)
       document.cookie= name + "="+cval+";expires="+exp.toGMTString();
}