Drop `toggleClass(boolean)` and `toggleClass(undefined)` signatures

[silverwind]

Can we evaluate if these signatures can be dropped? Here's a few arguments:

• It can mask bugs when the first argument inadvertently evaluates to undefined, which results in all classes being removed the first time it is called.
• It's badly documented (Misleading documentation for toggleClass() method. #1696) and because of that, probably not well-known.
• The way it saves a __className__ data seems like a bad practice.
• For custom builds, it creates a otherwise unnecessary dependency for attributes/classes towards data.
• It would allow the following savings for full builds:

   raw     gz Compared to master @ 5b4cb0d33731a58384e02ad51e703e7dcb00e424
  -701   -230 dist/jquery.js
  -168    -61 dist/jquery.min.js

[silverwind]

Looks like I missed that the boolean signature was already deprecated in 3.0. I assume this means the undocumented undefined is also included?

Oh, and what's the target timeframe for removal? 4.0? I'd gladly submit a PR for its removal if the time is right.

[timmywil]

@silverwind yes, removal would be in 4.0

[timmywil]

And thanks for offering!

[silverwind]

Ok, I'll close this as I'm sure you have that planned. If you want to keep it as a reminder for removal, feel free to reopen.

[mgol]

I think it's good to have it as a reminder, we already have some issues created for 4.0.0 (https://github.com/jquery/jquery/milestone/7) but this one was missing.

[mgol]

Thanks for the report!

[mgol]

PR: #4766