On: Emulators written in JavaScript

Nice list. I do wonder how useful they are though, given that the actual ROMs for many games are illegal to distribute and the emulators require them to work. Are they for people running a personal server on their computer? For websites that want to let people play homebrew games through the browser?

Seems like the list of uses for a Javascript emulator isn't particularly high.

But they're pretty cool on a technical level.

The ROMs may be copyrighted of course, but there is an argument to be said for there being a fair use case here, namely archiving of historical content that is no longer accessible otherwise. That's what the Internet Archive nonprofit is doing, and it's very important,

https://archive.org/details/softwarelibrary_msdos_games

Also, is it legal to posses a ROM that you own physically? I would think legal precedents for archiving or ripping (format conversion) might apply.

> Are they for people running a personal server on their computer?

Many pure JS applications can be run via a file:// URI, so there's no need to set up dedicated infrastructure, other than "Open With -> Some Browser".

There's no reason a JavaScript emulator can't take a local file and run it in the browser, using the HTML5 File API.

That's not different in any way from an emulator written in a native language - the user supplies data to a runtime on their own hardware.