Yes! I logged in just to mention HOCON, then I noticed you have mentioned it already :- )

So, the project you linked to is Java / Scala: https://github.com/lightbend/config

And there're also (basic? complete?) HOCON parsers in Javascript and Rust — I investigated this a while ago, because I want to use HOCON everywhere in my projects:

https://docs.rs/hocon/0.5.1/hocon/ (Rust)

https://www.google.com/search?q=hocon+javascript (Js, a few different)

The Rust version:

> This implementation goal is to be as permissive as possible, returning a valid document with all errors wrapped in `Hocon::BadValue` when a correct value cannot be computed

How nice :- ) (it seems to me)