js的cookie类，很好！

var Cookie = {
    createCookie : function(name,value,days){   //创建cookie
        if (days) {
            var date = new Date();
            date.setTime(date.getTime()+(days*24*60*60*1000));
            var expires = "; expires="+date.toGMTString();
        }else{
            var expires = "";
        }
        document.cookie = name+"="+value+expires+"; path=/";
    },
    readCookie : function(name){    //读取cookie
        var nameEQ = name + "=";
        var ca = document.cookie.split(';');
        for(var i = 0;i < ca.length; i++){
            var c = ca[i];
            while (c.charAt(0)==' '){
                c = c.substring(1, c.length);
            }
            if (c.indexOf(nameEQ) == 0){
                return c.substring(nameEQ.length, c.length);
            }
        }
        return null;
    },
    eraseCookie : function(name){   //清除cookie
        this.createCookie(name,"",-1);
    }
}

Cookie.createCookie('myhost',location.hostname,7);