Something I wonder is, what happened to asm.js? It got killed by WASM. In a way this is good, WASM is a "better" solution, being a formal bytecode machine description, but on the other hand, asm.js would not have the same limitations e.g. with respect to DOM interaction, or debates on how to integrate garbage collection, since you stay squarely in the JS VM you get these things for free.

Basically in some ways it was a superior idea: benefit from the optimizations we are already doing for JS, but define a subset that is a good compilation target and for which we know the JS VM already performs pretty optimally. So apart from defining the subset there is no extra work to do. On the other hand I'm sure there are JS limitations that you inherit. And probably your "binaries" are a bit larger than WASM. (But, I would guess, highly compressible.)

I guess the good news is that you can still use this approach. Just that no one does, because WASM stole the thunder. Again, not sure if this is a good or bad thing, but interesting to think about... for instance, whether we could have gotten to the current state much faster by just fully adopting asm.js instead of diverting resources into a new runtime.