It's actually worst than that. It searches the entire DOM for 'joe' and
then loops through all 'joes' that are returned to see if they are one
of the ancestors. In Firefox, this is pretty fast (because it uses
Xpath) but in IE, when there are a lot of elements it gets really slow.
If you know the exact ancestor count, you could do $(you).up(1). This
is much faster than $(you).up('joe').
Trevan
Peter wrote:
> It's me. I realize it's me, but I just can't wrap my brain around it.
>
> So I have 120-ish form fields, and for each of the form fields I need
> to go up to the field's container div.
>
> I replaced a large chunk of DOM traversal code (recursive checks of
> parentNode until the correct condition is reached -- selector is
> matched -- approximately 2 iterations) with the Prototype code of
> $(element).up('div.field_control')
>
> That line looks about right.
>
> So (expect the so, it's a story) performance on the form took a huge
> hit (processing time increased by factor of 5 to 10).
>
> As I stepped through the code, I saw that Element.up used
> element.ancestors(), and ... well, it must be me.
>
> Analogy: I want to find your (yes, YOUR) most recent ancestor whose
> name was Joe. $(you).up('joe') -- right? Yes, given names are
> tagNames.
> It turns out that the procedure is to find all of your (I'm still
> talking about you) ancestors up to Adam (it's just a name; somebody
> had to kick it off) and then iterate through them to find the most
> recent match.
>
> I don't suppose there should be a way to shortcut the recursion to
> actually stop when a match is found instead of (in my case) 12 more
> recursion instances so that performance doesn't take a sevenfold hit
> (2 to 14 recursion instances) without sacrificing the beauty of the
> syntax. I sure wish there was though.
>
> I'm sure it's just something I'm missing, and I am fully ready to
> accept a logical explanation. I just need some help.
> >
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