Right, thanks. And I hope my question does not sound too critical. I was just genuinely curious why JS was used.
I think JS is fine for small to mid-sized tasks, prototyping and testing ideas. However, for real DNS servers, used by a lot of clients, I believe C, C++, Go or Rust would be an absolute requirement.
The JS implemention is a fork of bcoin, the JS Bitcoin full node and production backend.
It binds to libunbound but you are right that you would want a lower level language for it to be more scalable. There is a rust implemention work in progress here:
https://github.com/UrkelLabs/rsd
This is separate from the DNS resolver being written in JS, but the team behind Handshake also created bcoin, which is the only javascript fullnode (and non-core fullnode IIRC) that has mined a Bitcoin block.
I think JS is fine for small to mid-sized tasks, prototyping and testing ideas. However, for real DNS servers, used by a lot of clients, I believe C, C++, Go or Rust would be an absolute requirement.