Jan de Jager has published e486-web on GitHub, an Intel 80486DX2-66 PC emulator written entirely in ES6 JavaScript. It runs in the browser with no dependencies and no build step.

The emulator covers the CPU, the motherboard, and modular ISA and VLB adapter cards. It boots real unmodified firmware: SeaBIOS and a VGA BIOS, then FreeDOS 1.3 on top. From there it runs DOS games including Commander Keen 4, Wolfenstein 3D, Duke Nukem II, and DOOM.

Setup is a static HTTP server started in the project root, then opening localhost in a browser. That is the whole install.

See more on GitHub.