If you have any concerns about performance of your web application, you probably should read this. Some times ago i read on a site (don’t remember which, was like AGES ago) that a good performance improvement is to be VERY specific when you use a library to select an element from the DOM. That article was written with Prototype in mind but i’ve though that will work same for jQuery as well. HUGE MISTAKE!

Kinda obviously, jQuery is NOT Prototype and they seems to NOT work in the same manner. Today i think to test the results of various selector. For this, i used Profiler from Firebug (what? you don’t know what firebug is?). And i was amazed. And i mean AMAZED!

I made this test right on this blog. I used jQuery('li') in console and, after that i used jQuery('ul li') (there is 24 LI elements on the first page). Until today i think the second option is faster. Why? Well.. Is more specific, isn’t it?

The second pick is around 2.6 times SLOWER than first one. (0.533ms vs 0.205ms).

Unfortunately, i’ve try to use the slower technique on many projects. But, lucky me, for no reason, i always forgot to do that (and i use to remember too late)

So, be careful! Don’t make this mistake If somebody will tell ya that a method is faster, DON’T take his word as a law. TEST IT!