TeaVM – Ahead-of-time transpiler of Java bytecode to JavaScript or WebAssembly
For the reverse, I wrote a WASM-to-JVM compiler: https://github.com/cretz/asmble.I think WASM has the ability for us to finally cross the language boundaries without marrying ourselves to C/C++ ABI. But at this early stage, there's no common stdlib for all languages to share.