Great demo.

A couple of years ago, I wrote a Javascript implementation myself: https://github.com/avik-das/js-raycast

And then, when asm.js (precursor to WebAssembly) became a thing, I rewrote it in C and compiled it to asm.js: https://github.com/avik-das/emcc-raycast

I'd already written a ray tracer (so a fully 3D renderer) prior to that in college, so it was fun to learn about a more limited algorithm that was better suited to older hardware.