[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:  joemcgill
     Type:  enhancement                    |      Status:  closed
 Priority:  high                           |   Milestone:  6.3
Component:  Script Loader                  |     Version:  4.6
 Severity:  normal                         |  Resolution:  fixed
 Keywords:  has-patch commit has-dev-note  |     Focuses:  performance
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Comment (by westonruter):

 In [changeset:"56933" 56933]:
 {{{
 #!CommitTicketReference repository="" revision="56933"
 Script Loader: Move delayed head script to footer when there is a blocking
 footer dependent.

 This prevents a performance regression when a blocking script is enqueued
 in the footer which depends on a delayed script in the `head` (with
 `async` or `defer`). In order to preserve the execution order, a delayed
 dependency must fall back to blocking when there is a blocking dependent.
 But since it was originally delayed (and thus executes similarly to a
 footer script), it does not need to be in the head and can be moved to the
 footer. This prevents blocking the critical rendering path.

 Props adamsilverstein, westonruter, flixos90.
 Fixes #59599.
 See #12009.
 }}}

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Ticket URL: <https://core.trac.wordpress.org/ticket/12009#comment:164>
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