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Opened 8 years ago

Last modified 2 months ago

#12009 reopened enhancement

Add support for HTML 5 "async" and "defer" attributes — at Initial Version

Reported by: Otto42 Owned by: azaozz
Milestone: Future Release Priority: normal
Severity: normal Version: 4.6
Component: Script Loader Keywords:
Focuses: Cc:


HTML5 supports async and defar attributes on script tags: http://www.w3.org/TR/html5/semantics.html#attr-script-async

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.

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