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