One of the more interesting projects I’ve worked on recently is using emscripten to port PetaGene’s high-performance decompression suite to wasm so that it can run in a browser with no installation.
It required figuring out how where to draw the line between having a fully async API (ideal for javascript) and using Emscripten’s asyncify to emulate synchronous IO (ideal for standard C/C++ applications). It also required an ill-thought-out optimization to igv.js, which prompted a much better fix by the maintainer. This is why I like the OSS model: even bad ideas can prompt a discussion about better ones.