var User = function(id, name, pass) {
    var Obj = new Object(); // veya var Obj = {};
    Obj.id = id;
    Obj.name = name;
    Obj.pass = pass;

    Obj.write = function(x) {
        document.write(this[x]);
        return this;
    };

    Obj.str = "";
    Obj.serialize = function() {
        this.str = "{\"id:\""+ this.id +", \"name\":\""+ this.name +"\", \"pass\":\""+ this.pass +"\"}";
        return this;
    };

    Obj.out = function() {
        document.write(this.str);
        return this;
    };

    return Obj;
}

var user = User(1, "Kerem", "shG9011");
user.serialize().out().write("name");