There is a project called Retroarch that provides an emulator frontend to various emulator back ends. One of those back ends is Mupen64/Parallel N64. And retroarch and many of its cores are already compiled to WebAssembly, with a layer that binds to WebGL.
Read the article at medium.com.
HTML5 Game Developer, Enclave Games indie studio founder, js13kGames competition creator and Gamedev.js Weekly newsletter publisher. Mozilla Tech Speaker, Gamedev.js community firestarter. Organizes meetups / workshops / hackathons in Poland, is passionate about new, Open Web technologies, and excited about WebVR with A-Frame. Likes eating sushi and playing Neuroshima Hex.