I don't think you could make filter() work with the same approach, because it seems like you'd actually have to do computation on the result.

map() works for cases where you don't need to compute anything in the callback, you just want to pipeline the elements into another RPC, which is actually a common case with map().

If you want to filter server-side, you could still accomplish it by having the server explicitly expose a method that takes an array as input, and performs the desired filter. The server would have to know in advance exactly what filter predicates are needed.