Core: Drop support for IE (all versions)

[mgol]

Summary

This PR is to show what dropping IE support would look like in code. If we make a decision to drop IE in v4, this PR can be merged, guarded on possible review remarks. EDIT: we've decided to land this in 5.0.0.

Of course, dropping IE would open a lot of other doors for various refactors but those would be considered separately.

Size difference:

main @063831b6378d518f9870ec5c4f1e7d5d16e04f36
   raw     gz Filename
 -1969   -608 dist/jquery.min.js
 -1763   -553 dist/jquery.slim.min.js
 -1969   -609 dist-module/jquery.module.min.js
 -1763   -556 dist-module/jquery.slim.module.min.js

Checklist

• New tests have been added to show the fix or feature works
• If needed, a docs issue/PR was created at https://github.com/jquery/api.jquery.com

[mgol]

Firefox doesn't have the behavior from the above comment (click events are not fired for non-primary mouse buttons) so perhaps this all could be removed. But one of our tests checks this condition explicitly so I'd rather leave it for a separate PR.

[mgol]

This file has been broken for a long time due to the use of live… But it looks potentially useful so I fixed it.

[dmethvin]

Seems like the right move at this point. Things clean up nicely!

[ollie-iterators]

The blog about jquery 3.7.0: https://blog.jquery.com/2023/05/11/jquery-3-7-0-released-staying-in-order/ says that "support for IE will be dropped in jQuery 4.0"

[mgol]

@ollie-iterators Thanks for the info; that should say 5.0; we’ll fix it.

[vrubleg]

It's 2023, IE11 is 10 years old, half of the web already doesn't work in this browser. IE11 was introduced with Windows 8.1 that is already not supported by a lot of software (including Firefox and Chrome) and libraries (like Qt6+ or Python 3.9+). It makes sense to drop IE earlier.

[mgol]

@vrubleg I understand the sentiment and I admit more than a year has passes since I raised this PR but I really don't want to make any changes to our 4.0.0 plans at this point as any further change is just going to delay the whole thing, and it's already been delayed a lot.

I want to get the beta out with only our current blockers resolved. Once we have that, once we also have the respective Migrate release and the upgrade guide prepared, we can talk about it once again.

[nagyimre1980]

IE drop 4.1.0 ?

[mgol]

@nagyimre1980 No; we treat reducing browser support policy as a breaking change so it has to land in a major version update.