关于javascript:对js添加cookie的函数封装

addCookie("age","21");
    //后三个参数为可选项
    function addCookie(key,value,day,path,domin) {
        //1.解决保留的门路
            //找到html文件前的 / 索引
        var index = window.location.pathname.lastIndexOf("/");
        var currentIndex = window.location.pathname.slice(0,index);
        path = path || currentIndex;
        //2.解决默认保留的domin(域名)
        domin = domin || document.domin;

        //3.解决输出的工夫
        if (!day){
            document.cookie = key + "=" + value + ";path=" + path + ";domin=" + domin;
        }else {
            var date = new Date();
            date.setDate(date.getDate() + day);
            document.cookie = key + "=" + value + ";expires=" + date.toGMTString() + ";path=" + path + ";domin=" + domin;
        }
    }