Can you make @Quy happy, then we can merge it.

@laoneo done

Thanks!

I'm struggling to follow this issue and can't see if jQuery is being dropped from Joomla 4.0 or not. On Bootstrap's Twitter feed on 2nd January they said: "As we start thinking about v5, what should we remove from Bootstrap? Already dropping jQuery and very likely IE10/11 in our next major version."

@Scrabble96
JQuery library will be provided by the J4 package and you can load it with simple HTMLHelper code lines like before. The same with Twitter Bootstrap.

But the deep JQuery and Bootstrap dependencies like we know them from J3 are removed from J4 core code as far as possible. Freedom of choice for extension and template developpers in J4.

@ReLater
Thank you. I notice, though, on analysing a website using cassiopeia (alpha 7.0-dev nightly build 11/12 Jan) that this file is loading by default from /media/vendor/jquery/js/jquery.min.js?3.3.1 as well as /media/vendor/bootstrap/js/bootstrap.bundle.min.js?4.1.3 and /media/legacy/js/jquery-noconflict.min.js?5cc8741ba543bcb5a55a949fd0617415

I can't see where the instruction to include these files is in the cassiopeia template files in order to be able to exclude them; i.e. the 'freedom of choice' you mention.

The templates right now are forcing both jquery and bootstrap.js. This is wrong and will be fixed as soon as the remaining dependencies get removed

I can't see where the instruction to include these files

New magic in J4

$wa   = $this->getWebAssetManager();
$wa->enableAsset('template.cassiopeia.' ... and so on ...

in combination with file joomla.asset.json

Sup. On the new administrator/components/com_fields/helpers/fields.php line 350

replace if (!element.val() !== "$assignedCatids") { with if (!element.value !== "$assignedCatids") {

That's the only jQuery thing I've yet noticed in the PR.

EDIT:
Also, you can speed up the backend/frontend load BIGTIME by removing DOMContentLoaded listeners and adding ALL those scripts in the <footer>.