There's TeaVM[0], which is an old project that compiles JVM bytecode to JS, and more recently, also to WASM. I had thought the project had been abandoned, but

There's TeaVM[0], which is an old project that compiles JVM bytecode to JS, and more recently, also to WASM. I had thought the project had been abandoned, but I was wrong, it seems to be actively maintained and evolving on GitHub[1]. [0] http://teavm.org http://teavm.org [1] https://github.com/konsoletyper/teavm/issues https://github.com/konsoletyper/teavm/issues