There’s a great list over at Github of about 50 emulators written in Javascript.
I’ve pasted the list below, but special thanks to Frederic Cambus who compiled the list.
Amstrad
Apple
- Apple IIjs – An Apple ][ Emulator in JavaScript
- a2 – A fast, WebGL optimized Apple ][+ emulator.
- Apple2JS – A JavaScript emulator for the Apple II