What libraries exist for doing things with audio? How complicated would it be to make a game in JS? How accessible is Electron?
Great question! Glad people are getting interested!
Electron is pretty easy to setup. It's all done through the command line, and the tools are accessible.
There is a library called Sono which makes creating audio games pretty easy. For input I simply use JQuery, even though that's probably already overkill.
You're just gonna have to be aware what you're getting yourself into. This is a constantly changing thing, and implementations vary quite a bit from browser to browser, so it's going to be a fight sometimes figuring out what works, reporting issues, etc.
I'm working on a lane splitter type game for the browser. It should be done in relatively short time, week or two. You can take a look at the source if you're interested when it's up.
Is it possible to test offline, or are we still in the "must load from server" security mode?
I always test with a simple express server running in node, but you could use things like xampp if you want. The libraries make requests and you need something to answer them.