我不知道是什么意思加藤。但现在，我明白承诺的解决方案是pretty直截了当：

I didn't realize what Kato meant. But now that I understand promises the solution is pretty straight forward:

    register: function (user) {
        return auth.$createUser(user.email, user.password)
            .then(function() {
                return auth.$login('password', user);
            });
    },