Stricter typings for on and emit on client and server sides

[david-fong]

Here is a TypeScript Playground link for an idea I've been thinking about for a while.

Here is a link to the project repo.

It allows to specify explicit typings / function signatures for on and emit. This could be used to enable the compiler to warn when the arguments are not being passed properly. I like the "Upstream" / "Downstream" dictionary interface. Try it out for yourself and share what you think. Is this something you think you could benefit from?

The next thing I will add is an optional last argument for an ack function.

[darrachequesne]

For future readers:

This was implemented in 0107510, included in version 4.0.0 🚀

Documentation: https://socket.io/docs/v4/typescript/