[JS] Class static block available by default

[Rumyra]

Acceptance Criteria

• The listed features are documented sufficiently on MDN
• BCD is updated
• Interactive example and data repos are updated if appropriate
• The content has been reviewed as needed

For folks helping with Firefox related documentation

• Set bugs to dev-doc-complete
• Add entry to Firefox release notes if feature is enabled in release
  or
• Add entry to Firefox experimental features page if feature is not yet enabled in release

Features to document

Class static blocks - see https://github.com/tc39/proposal-class-static-block which is helpful. Check classes & static docs for updates

Related Gecko bugs

https://bugzilla.mozilla.org/show_bug.cgi?id=1725689

[hamishwillee]

@Rumyra, JavaScript is mad. I'll at least start this, but will need your review.

So I think this is worth having its own topic under classes - Classes > Class_static_initialization_blocks. Probably also updates to Classes > static and maybe Classes >Static methods and properties.
Might need to be mentions in Classes > Public_class_fields (not so sure on that).

Some really useful resources, particularly the first one:

• https://2ality.com/2021/09/class-static-block.html - good worked example
• V8 explainer: https://v8.dev/features/class-static-initializer-blocks
• Original proposal: https://github.com/tc39/proposal-class-static-block
• v8 release note: https://v8.dev/blog/v8-release-94 (planned for Chrome 94)

Status:

• BCD: JS class static inititialization blocks browser-compat-data#12508
• Interactive example: Add class static initialization block example interactive-examples#1918
• Release note: FF93 Relnotes: Class static initialization blocks #9310
• Docs - Class static initialization blocks #9281
• Dev-doc-complete

[Rumyra]

@Rumyra, JavaScript is mad.

Yup /me nods wildly

I thought this might be a bit of work. I'll come back to it first thing on Monday to check through the above properly.

Happy for you to get started and I'll try and support as best I can 👍

[hamishwillee]

@Rumyra Great. I did a first draft in #9281 - I am kind of hoping that if you don't like that you will take the job over. I spent a lot of time on this today. I do NOT think it is hard - I think I'm just not particularly experience in JavaScript and the time remaining for this cycle is short.

I decided that https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Classes/static would be a good place for this, but it would end up hiding the 80% people need most. So in the end I created a new doc for this and linked.