An alternative is metacall. The example in the readme is about calling Python from Javascript, but it also works with other languages, like Ruby, C#, Java, and other languages
In the future, maybe webidl (or extensions of it) will bring interoperability between languages too. At the moment there is https://mozilla.github.io/uniffi-rs/ for interoperability between Rust and a number of languages (basically the ones mozilla needs: Swift, Kotlin, Javascript)
https://github.com/metacall/core
List of supported languages here https://github.com/metacall/core/blob/develop/docs/README.md...
In the future, maybe webidl (or extensions of it) will bring interoperability between languages too. At the moment there is https://mozilla.github.io/uniffi-rs/ for interoperability between Rust and a number of languages (basically the ones mozilla needs: Swift, Kotlin, Javascript)