Not sure about Kotlin, but there is alreadt CheerpJ that can run Java applets unmodified both as normal JS, or as WASM. For non-applets there is even more poss

Not sure about Kotlin, but there is alreadt CheerpJ that can run Java applets unmodified both as normal JS, or as WASM. For non-applets there is even more possibilities: there is google’s closure compiler and teawm, both can produce really great code!