[wp-trac] [WordPress Trac] #12009: Add support for HTML 5 "async" and "defer" attributes

[WordPress Trac]

#12009: Add support for HTML 5 "async" and "defer" attributes
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 Reporter:  Otto42         |       Owner:  azaozz
     Type:  enhancement    |      Status:  reopened
 Priority:  normal         |   Milestone:  Awaiting Review
Component:  Script Loader  |     Version:  4.6
 Severity:  normal         |  Resolution:
 Keywords:                 |     Focuses:
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Comment (by seancjones):

 I think this is an important issue to resolve. As of now, Google Page
 Speed Insights failing for a lot of WordPress installs can almost
 exclusively be blamed on render-blocking JavaScript. Fixing that increases
 speed by wide margins.

 Plugin developers should have a way of deferring page loads. There are
 clear pitfalls to avoid - like people's websites breaking.

 I'm going to play devil's advocate and argue why a filter might be better.

 A filter allows a user with a code sample to defer scripts, or remove
 scripts if they appear to break their current setup. Plugin developers can
 send an array of script handles to defer via a plugin, rather than rewrite
 their code with a new parameter.


 If a user wanted to disable all deferring:

 {{{
 add_filter ( 'wp_defer_scripts', function($wp_defer) {
   return array();
 }, 900, 2 );

 add_filter ( 'wp_async_scripts', function($wp_async) {
   return array();
 }, 900, 2 );
 }}}

 For someone to enable all hooks:

 {{{
 add_filter ( 'wp_async_scripts', function($wp_async) {
     global $wp_scripts;

     return $wp_scripts->queue;
 } );
 }}}

 This would also make it far easier for plugin developers to patch their
 plugins.

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Ticket URL: <https://core.trac.wordpress.org/ticket/12009#comment:33>
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