jQuery Forum

I have noticed similar problems, too, with all manner of effects.  Usually happens only once.  And the explanation is simple:  JS needs to be compiled before it can run.  Browsers don't compile the entire code base but will instead compile on demand.  Saves time if large portions of code never run.  The flip side is that early animations take a performance hit (as the browser is busy compiling).  This gets worse the slower the user's computer.  If this is critical, make sure your code does a dry run.  It's a little like pre-fetching images.  In your case, run your animation first on some invisible element somewhere.  On the second - real - run, things will likely look a lot more homogeneous across different browsers.

Thanks for your response.

Interesting point about compiling and running on invisible element first. Is this an established practice - never heard of such. Is there any insightful resource on this?

Dunno.  As I said, my app suffers from this too.  Hasn't bothered me to date.  I have far greater fish to fry :-(  I am sure that now that I've drawn your attention to it, you will notice the effect in any number of places if you pay close attention.  Particularly apparent, for example, on JS includes that are used by certain panels only.  First time you open such a panel, it stutters a little.  No big deal.  Though I understand that it can be noticeable during graphical transitions.

I tried to run an effect on invisible element first, but it doesn't look to eliminate choppy movement on visible one later on. So I guess it doesn't work that way. I'm not that competent actually, but I've never heard that browser does compile javascript, I thought it was always interpreting it. Is not that true?

:-))  You say compile, I say interpret - lets call the whole thing off.

No compile and interpret are not the same. Of course browser may compile JavaScript for itself and keep somewhere, but I never encountered this mentioned anywhere. I think if it could be forced somehow it would be very popular technique around the web.

If I repeat effects several times, sometimes they are smooth sometimes not and it doesn't look like it depends on whether it is first time or not.

Can anyone else confirm or object this please, I think it's pretty important point?