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

WordPress Trac wp-trac at lists.automattic.com
Mon Jan 25 16:40:29 UTC 2010

#12009: Add support for HTML 5 "async" and "defer" attributes
 Reporter:  Otto42       |       Owner:  azaozz    
     Type:  enhancement  |      Status:  new       
 Priority:  normal       |   Milestone:  Unassigned
Component:  JavaScript   |     Version:            
 Severity:  normal       |    Keywords:            
 HTML5 supports async and defar attributes on script tags:

 Basic usage of these:

 - "async" scripts get executed asyncronously, as soon as they're loaded.
 This lets them run without slowing down the page parsing (normally, all
 page processing stops while the javascript code is executing).

 - "defer" scripts get deferred from running until page processing is
 complete. Sorta like jQuery(document).ready() does, except without pre-
 definitions. Faster, in other words, since it's built into the browser.

 Correct usage would dictate that "libraries" like jQuery and such would
 get the async attribute, while bits of code that use the current DOM would
 get deferred. The defer bit is basically optional though, since most all
 code that exists uses something like jQuery(document).ready() already,
 when it's necessary, and so there's not a lot of benefit there.

 The just released Firefox 3.6 supports the async attributes, so you can do
 testing with these immediately. I've noticed a speedup on the wp-admin
 side of things by using it, but I have not measured this and cannot be
 sure I'm not imagining it. Still, it does seem like it makes the page
 appear faster.

Ticket URL: <http://core.trac.wordpress.org/ticket/12009>
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