Nim is a fun language to program and also meets some of your requirements. It can compile to JS and has some libraries to interop with html. Admittedly it’s a bit limited on those packages but they exist.

HTML template: https://github.com/juancarlospaco/nim-html-dsl

SDL on emscripten: https://jipok.github.io/Nim-SDL2-and-Emscripten/