Comments on: Finding Element Positions

By: Altay Guvench

Altay Guvench — Tue, 14 Aug 2007 01:49:26 +0000

Hey Ryan, I’m joining the discussion a little late, but this seemed worth pointing out. Don’t the hasClassName and previousSiblings methods call Element.extend on the node? Apparently, that’s a LOT slower in IE than other browsers, and the source of a many IE/Prototype bottlenecks: http://groups.google.com/group/prototype-core/browse_thread/thread/aecbf8e008782d6a

It seriously adds up over 800 iterations. I love prototype as much as the next guy, but try a vanilla comparison in your loop (e.g. if (elt.className==’target’) …). Not only will this be faster in all browsers but — most importantly — IE does it almost as fast as Firefox!

If you wanted to be a little fancier, maybe you could do $(‘lis’).getElementsByTagName(‘li’), and extend ONLY the resulting array — rather than every single node in the array. Then you can use prototype’s Array.indexOf method.

By: Ryan Campbell

Ryan Campbell — Fri, 27 Jul 2007 02:30:51 +0000

The test was actually run with the target being #800. I haven’t done any official testing, but I believe that previous siblings is always faster.

By: Alex Soto

Alex Soto — Fri, 27 Jul 2007 00:54:00 +0000

It would be interesting to see if it makes a difference where the target is in the list. Would the previous siblings be slower if the target element was at the end of the list (#800) as opposed to early in the list?

By: Ryan Campbell

Ryan Campbell — Thu, 26 Jul 2007 14:04:45 +0000

The Firefox and Safari 3 tests were done on the same machine. Then, the Safari 3 test was redone on a Windows machine, and the speed was very similar. That machine then ran the IE tests. It might not be 100% accurate, but I would imagine IE6 is still much slower at these types of operations.

By: Colm

Colm — Thu, 26 Jul 2007 08:34:00 +0000

What tool did you use to test the time?

Also wouldn't the spec's of the machines (memory, processor) dictate the speed?

By: AsiaPartTime

AsiaPartTime — Wed, 25 Jul 2007 23:57:38 +0000

Good guide for me to loop list. but my company don’t allow to use Prototype librayr :(

By: Ryan Campbell

Ryan Campbell — Wed, 25 Jul 2007 17:14:39 +0000

They were done with version 1.5.1.1.

By: Andrew Dupont

Andrew Dupont — Wed, 25 Jul 2007 16:58:39 +0000

Those benchmarks suggest to me that we haven't fully optimized methods like previousSiblings. Such methods take an optional CSS-selector argument to filter with, but when the argument is omitted there shouldn't be a Selector query at all. (Were these benchmarks using the latest version of Prototype?)

Maybe IE is just really slow with this sort of task â€” your other approaches yield nearly identical results â€” but when I see such a disparity between IE and Firefox/Safari I immediately suspect a Selector query. I'll look into this.