Comments on: Improve your jQuery Selectors: 5 Quick Tips

By: David O'Trakoun

David O'Trakoun — Fri, 09 Jul 2010 16:18:40 +0000

I’d have to look at the source again but I think the discrepancy here is between sizzle and jquey. Jquery’s find is a wrapper for sizzle, whereas jquery(“selector selector”) will iteratively call .find() — sizzle — in the order of jquery’s logic

By: Nathan J. Brauer

Nathan J. Brauer — Fri, 02 Jul 2010 10:39:07 +0000

Actually, it’s my understanding that sizzle goes both ways. Take this as an example:

jQuery(“div.header ul”)

It will first look for all “ul” nodes.
Then within that list, it will make sure one of its parents is a “div” node
Lastly it will narrow those nodes down to the class (“.header”)

Thus, it is faster to do this:
jQuery(‘ul’,'div.header’)

Which is equivalent to this:
jQuery(‘div.header’).find(‘ul’)

——
Or the other way around:
jQuery(“div.tasks p.urgent”)
1. looks for all ‘p’
2. narrows all p’s to .urgent
3. makes sure one of its parents is a div node
4. makes sure one of its div parents has .tasks class

Better:
jQuery(‘p.urgent’,'div.tasks’)
same as:
jQuery(‘div.tasks’).find(‘p.urgent’)

Let me know if I’m wrong

By: Ricardo Rodrigues

Ricardo Rodrigues — Fri, 02 Jul 2010 08:21:29 +0000

Good article, I have only two comments:

1) The Avoid Extra Traversing second code block is missing one double quotation mark

2) On the var myElement = $(“div#elem”); piece of code, you didn’t use the $varName, meaning preceding a jQuery object variable with the dollar sign, but you didn’t below, I use this all the time and it’s a readability candy!

By: David O'Trakoun

David O'Trakoun — Thu, 01 Jul 2010 15:00:05 +0000

@Mike

Your expectations are actually correct regarding Sizzle.find
the default setting for Sizzle is to use ID specificity first
after which it goes from left to right

see http://wiki.github.com/jeresig/sizzle/

By: Andreas Grabner

Andreas Grabner — Thu, 01 Jul 2010 11:56:59 +0000

Unfortunately the latest versions of IE (6, 7 & do not support getElementsByClassName – therefore I believe the author is spot on. Of course – if you only develop for modern browsers than this is a different deal – but – I guess that every web app out there will still get a lot of hits from IE – and you need to care about them too.

By: Ain

Ain — Thu, 01 Jul 2010 09:43:12 +0000

The author is well wrong in point one about the class selectors. Select by class is optimised on modern platforms, WebKit added support for getElementsByClassName back in 2007: http://tekkie.flashbit.net/browsers/webkit-adds-getelementsbyclassname

By: Maicon Sobczak

Maicon Sobczak — Wed, 30 Jun 2010 12:18:20 +0000

Valuable tips. Specially about contextual information.