Me too, so do I: cũng vậy / cũng thế

To say that the same goes for you, without repeating the whole sentence, say your word for "I" and then cũng vậy: Em cũng vậy. Me too. In Hà Nội it's cũng thế: Em cũng thế.

It follows any statement, positive or negative, so it covers "me too", "so do I" and "me neither". If a friend says Mình đói quá, then Mình cũng vậy means "Me too". If she says Mình không biết bơi, the same words mean "Me neither". For "me neither", many people also simply say cũng không: Mình cũng không.

It isn't only for "I": Chị Lan cũng vậy (Lan too), Ở đây cũng vậy (it's the same here). It also answers a good wish, like "you too": when someone says Chúc em cuối tuần vui vẻ! (have a good weekend!), you can reply Chị cũng vậy nha!

Cũng vậy is the quick reply. To say exactly what, repeat the verb with cũng: Em cũng thích (I like it too). On its own, vậy means "so" or "like that"; như vậy, "like that", is a later pattern.