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Re: [whatwg] Proposal: Adding methods like getElementById and getElementsByTagName to DocumentFragments

From: Tab Atkins Jr. <jackalmage@gmail.com>
Date: Fri, 18 Oct 2013 12:11:15 -0700
Message-ID: <CAAWBYDCCXtT242e1-gPKvd_z7PO_Ki8-+tK5DUBRuWjbNUf0uA@mail.gmail.com>
To: James Greene <james.m.greene@gmail.com>
Cc: Glenn Maynard <glenn@zewt.org>, Ryosuke Niwa <rniwa@apple.com>, whatwg <whatwg@lists.whatwg.org>, Tim Streater <tim@clothears.org.uk>, Boris Zbarsky <bzbarsky@mit.edu>, Ian Hickson <ian@hixie.ch>
On Fri, Oct 18, 2013 at 11:09 AM, James Greene <james.m.greene@gmail.com> wrote:
> I would also love to see `getElementById` added to the HTMLElement/Element
> interface. It would be nice to capitalize on that potential perf boost in
> jQuery as well.

There's no perf boost available for searching by id on an arbitrary
element.  The reason you may get a better perf for the normal
functions is that documents cache a map from id->element on
themselves, so you just have to do a fast hash-lookup.  Arbitrary
elements don't have this map (it would be way too much memory cost),
so it'll fall back to a standard tree search, exactly as a
querySelector would.

~TJ
Received on Friday, 18 October 2013 19:11:59 UTC

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