Allow user to specify supported events (TypeScript)

[ZLima12]

This would allow users to verify that they only use events that they intend to.

e.g.

type AnyEvent = "ready" | "error" | "message";
class Foo extends EventEmitter<AnyEvent> { ... }
let instance = new Foo();
instance.on("ready", () => doSomething()); // Works fine
instance.on("bar", () => doSomething()); // Error

[lpinca]

cc: @delta62

[delta62]

Hey, @ZLima12. This is a great idea! I'm curious though - why did you decide to change the types in the functions to (string | symbol) & EventTypes instead of just EventTypes?

[ZLima12]

@delta62 As far as I know, the library itself only supports strings and symbols for events. If we only use EventTypes, it will allow the user to specify events that aren't strings or symbols. However, the type (string | symbol) & EventTypes will match any type that is both a string or symbol (to maintain compatibility with the library), and one of the types that the user specified.

[delta62]

Ok, that makes sense. I'd like to play around with something like

declare class EventEmitter<EventTypes extends string | symbol>

and see if that works. I'll try to do that today. If we can't come up with a way to do that, I think that your approach is good.

[ZLima12]

@delta62 how does that look?

[delta62]

Whoops, I missed your reply. Sorry!

I'll use this with my test project and add some examples to make sure we're not breaking anything, but I think this will work out nicely! 👍

[ZLima12]

Sorry again about being oblivious to @delta62 's thread on my fork, but I believe this should be ready to merge now.

[delta62]

[lpinca]

Thank you!