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

[James Greene]

>
> 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.


Hmm, I suppose that makes sense.  Bummer. Thanks for the concise
explanation!


Sincerely,
    James Greene



On Fri, Oct 18, 2013 at 2:11 PM, Tab Atkins Jr. <jackalmage at gmail.com>wrote:

> On Fri, Oct 18, 2013 at 11:09 AM, James Greene <james.m.greene at 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
>