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Re: Allow to return same NodeList object for queries like getElementsByTagName, getElementsByClassName and getElementsByName

From: Maciej Stachowiak <mjs@apple.com>
Date: Tue, 02 Feb 2010 17:02:03 -0800
Cc: public-webapps@w3.org
Message-id: <72366B4F-DD30-4A12-A242-41DBCB1B7D7B@apple.com>
To: Anton Muhin <antonm@chromium.org>
Hey folks,

Any thoughts on this? I think it would be wise to issue an errata against DOM 3 Core to allow caching of NodeLists, and make sure to fix this in DOM4. IE and Firefox seem to do it, and it can be a big performance benefit, so I think the DOM spec should allow it.

The three errata needed would be:

http://www.w3.org/TR/DOM-Level-3-Core/core.html#ID-A6C9094
Change return value of getElementsByTagName on Document from:
 "NodeList A new NodeList object containing all the matched Elements."
To:
"NodeList A NodeList object containing all the matched Elements."

http://www.w3.org/TR/DOM-Level-3-Core/core.html#ID-getElBTNNS
Change return value of getElementsByTagNameNS on Document from:
 "NodeList A new NodeList object containing all the matched Elements."
To:
"NodeList A NodeList object containing all the matched Elements."

http://www.w3.org/TR/DOM-Level-3-Core/core.html#ID-A6C90942
Change return value of getElementsByTagNameNS on Element from:
 "NodeList A new NodeList object containing all the matched Elements."
To:
"NodeList A NodeList object containing all the matched Elements."

If we agree to these errata, I would also suggest that related methods in HTML5 (getElementsByName, getElementsByClassName) should be consistent and should also not require a new NodeList every time.

Does anyone disagree?

Regards,
Maciej

On Jan 22, 2010, at 5:11 AM, Anton Muhin wrote:

> Good day.
> 
> Currently DOM core 3 spec is somewhat inconsistent regarding if
> invocations of getElementsByTagName and alike must return a new
> NodeList or could cache this list.  For Document it's mandated for
> both getElementsByTagName and getElementsByTagNameNS, but for Element,
> it's only worded for getElementsByTagNameNS, but not for
> getElementsByTagName.  Maciej noticed as well difference between
> getElementsByTagName and other getElementsBy queries (see
> http://www.w3.org/Bugs/Public/show_bug.cgi?id=8792).  And word "new"
> is missing from ECMAScript bindings spec:
> http://www.w3.org/TR/DOM-Level-3-Core/ecma-script-binding.html
> 
> Is it possible to allow caching for those cases?  Firefox caches those
> node lists for a long time (Maciej found the related bug
> https://bugzilla.mozilla.org/show_bug.cgi?id=140758).  IE8 caches as
> well.   Opera, Safari and Chrome do not.
> 
> Performance-wise it's a notable win (the less js objects one needs to
> create, the more efficient and less memory consuming browser one
> gets).  Given that node lists are live, what are the reasons for
> mandating creation of new object per query?
> 
> yours,
> anton.
> 
> 
Received on Wednesday, 3 February 2010 01:02:37 GMT

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