Calling all javascript/jquery expert - How Does Firefox processes javascript

Question

Hi,

I just created an image gallery at http://nu-lightbox.appspot.com/, a google app engine. I tested this website with firefox 3.5 in Windows XP and Ubuntu Linux. If you open the website and click on the circular blue arrowed button, you will notice how jaggy (not smooth) the animation is.

The weird thing is when I open the HTML page in my local box,not through google app engine, the animation is very very smooth.

From what I understand is that a browser will cache/download an HTML page, its javascript, and any related style sheet to the user local box when they view a website. Based on this notion, there should not be any server side processing for my image gallery. All the processing should be done at the client side/ user browser locally in their box.

So I don't really understand why the animation runs smoothly when I run the HTML page locally, but there is so much lag when I view it through google app engine.

Cheers.

Answer 1

You're right if everything is cached on the client then they should run at the same speed.

I would use Wireshark or Fiddler to check the HTTP traffic to make sure you know what exactly is going on.

Answer 2

As per best practices put all JavaScript at the end of the page and all CSS in the HTML HEAD element.

I'm guessing you will see more consistent (and faster) page performance.

added in edit

Also, close all tabs on your browser and restart it. You can't tell anything about performance if you have buggy JavaScript running in another tab. (Chrome is better with this issue.)