[wp-trac] [WordPress Trac] #37817: Emoji code not loaded responsibly

[WordPress Trac]

#37817: Emoji code not loaded responsibly
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 Reporter:  superpoincare  |       Owner:
     Type:  enhancement    |      Status:  new
 Priority:  normal         |   Milestone:  Awaiting Review
Component:  Emoji          |     Version:  4.6
 Severity:  normal         |  Resolution:
 Keywords:                 |     Focuses:  performance
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Comment (by tollmanz):

 I would also like to recommend that the emoji script is loaded more
 responsibly. Proving the impact via WPT/Dev
 Tools/{$your_favorite_profiler} is really tricky and likely to lead to bad
 decisions. I recently observed a 3 second delay in HTML parsing due to the
 emoji load, but have had a heck of a time reproducing that same result.
 These types of tests are subject to network, hardware, site construction,
 and other random variance that makes specific questions like these nearly
 impossible to answer.

 The issue is that the JS is loaded in both a render and HTML parser
 blocking manner. This means that under the right conditions, the impact of
 this seemingly innocuous script could be quite dramatic. As developers,
 when we know best practices for a specific problem, we should default to
 those practices and argue to not do them if we are so compelled.

 I would recommend that we include an `async` attribute to the `script` tag
 that wraps the emoji JS, as well as add an `async` attribute to the
 `script` that it potentially loads (`defer` would be even better, but it
 does not enjoy great cross-browser support). Further, the script should be
 loaded in the `wp_footer`, instead of the `wp_head`.

 If there are compatibility concerns, we could add some filters to allow
 people to change the behavior. We should strive to follow best practices
 for performant loading of this script, regardless of how minor the impact
 may be.

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Ticket URL: <https://core.trac.wordpress.org/ticket/37817#comment:10>
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