[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:  10upsimon
     Type:  enhancement                          |      Status:  assigned
 Priority:  high                                 |   Milestone:  6.3
Component:  Script Loader                        |     Version:  4.6
 Severity:  normal                               |  Resolution:
 Keywords:  has-patch has-unit-tests 2nd-        |     Focuses:
  opinion                                        |  performance
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Comment (by mor10):

 Hello.

 `async` has significant use cases in situations where a script either
 needs to be front-loaded or has no impact on the DOM but benefits from
 being loaded early. Examples include:

 - tracking and analytics
 - independent processes like booting up webworkers
 - performance-critical scripts like cutting the mustard
 - event-driven scripts monitoring user interaction and input
 - offsite interactions like preloading API calls etc
 - loading fonts and other assets via JS (necessary for for-pay foundries
 etc)

 I can think of a myriad of cases where themes and in particular plugins
 would use `async` to front-load JS.

 Most importantly, loading JS in the header and using `async`/`defer` lets
 both the developer and the browser make better decisions about how to load
 the scripts.

 I wasn't here.

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Ticket URL: <https://core.trac.wordpress.org/ticket/12009#comment:103>
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