javascript performance discussion wanted

[Wendy Gibbons]

is javascript really that slow?

At work we are just starting to write a new ExtJS front end to our app and 2 gurus are doing all of the code reviews.
They are quibbling (my opnion) that i use the wrong type of for loop as a

for (int i=0;i<x;i++)

is more efficient than a foreach loop.

are they being sensible?>

[Gregg Bolinger]

There's quite a bit of information on this if you google it. The general consensus seems to be that foreach loops are slower. And it seems to be slower/faster depending on the browser. If your app is very front-end heavy then I wouldn't consider it to be "quibbling".

[Bear Bibeault]

Or is this just a case of premature optimization?

[Gregg Bolinger]

Bear Bibeault wrote:Or is this just a case of premature optimization?

Quite possibly. I would just say that if you know something is slow and there is already an alternative then why use the slow one? It just becomes something you have to go back and refactor later.

[Bear Bibeault]

Perhaps but in this case I've never seen a difference in performance that has had any visible effect.

For the record I use both styles -- choosing whichever seems to fit the situation better or improve the clarity of the code.

[Wendy Gibbons]

Thanks guys,I have done some reading and with the newer browsers it doesn't make that much difference but as we are mainly going over arrays, it makes it easier anyway.

And our front end is very very heavy, it makes HTML look and behave like swing (but with enough differences to keep you irritated).

[Eric Pascarello]

You are right that it does not make a difference anymore. Most bottlenecks come from poor design decisions and people refusing to change backends to fit the front end needs.

Eric