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Re: jQuery selector performance / jQuery Tester

by north-6 :: Rate this Message:

Hi Karl,

thanks for your reply.

I used jQuery tester in FF2 + 3, IE6, 7 + 8, Opera 9.64 and I think
also in Safari 4 (on my Win XP machine). The results were are all
kinda similar. Using the class selector was always fastest.

I just ran the following test (choosing jQuery 1.3.2 again):

test('#content a.submit');
test('a.submit');
test('.submit');
test('("#myDiv").find("span.myClass")');

The results in FF3:

#content a.submit: 0.448s
a.submit: 0.344s
.submit: 0.331s
("#myDiv").find("span.myClass"): 0.399s

The results for IE are a bit strange and different from my earlier
results.

IE6:

#content a.submit: 1.641s
a.submit: 1.438s
.submit: 4.172s
("#myDiv").find("span.myClass"): 4.484s

IE7 (IE Tester tool):

#content a.submit: 2.046s
a.submit: 1.922s
.submit: 4.969s
("#myDiv").find("span.myClass"): 4.562s

IE8 (also IE Tester tool):

#content a.submit: 0.25s
a.submit: 0.219s
.submit: 0.219s
("#myDiv").find("span.myClass"): 3.578s

So only using the class name is much slower here.

Looking at my earlier test and this one, "a.submit" (i.e.
element.myClass) has shown the best overall performance .

Any comments? :)

Cheers

On 2 Jul., 19:36, Karl Swedberg <k...@...> wrote:

> On Jul 2, 2009, at 8:45 AM, north wrote:
>
>
>
>
>
> > Hi,
>
> > I just tested all my jQuery selectors using the jQuery Tester (http://
> > jquery.nodnod.net), and the results seem to "contradict" one thing I
> > read in a performance article: that you should descend from the
> > closest parent ID when using classes in your selector (the article
> > says "April 09", so the latest jQuery version was already available).
>
> > In my tests, using just the class selector (like span.myClass) was
> > always fastest (sometimes twice as fast as #myDiv span.myClass), and
> > this in all browsers I tested, not just the ones supporting
> > getElementsByClassName.
>
> > Maybe descending from the closest parent ID becomes a factor when you
> > have a lot of elements on you page? Any experiences?
>
> > Thanks
>
> If the selectors aren't causing a discernible bottleneck, I wouldn't
> worry too much about optimizing them. Just out of curiosity, though,
> what happens if you do this:
>
> $('#myDiv').find('span.myClass');
>
> any faster?
>
> Also, which browser are you testing?
>
> --Karl

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Re: jQuery selector performance / jQuery Tester