CouchDB supports writing views in Erlang, if you prefer that. It's also faster than Javascript, although it changes some of the ordering semantics of the resulting views.

I decided to write my views[1] in Parenscript[2]. Might not be for everybody, but it makes them fit a lot better in the rest of the application.

[1] https://github.com/cicakhq/potato/blob/72e162a95332e8979d865...

[2] https://common-lisp.net/project/parenscript/