http://www.silverstripe.org/home/ http://www.silverstripe.org/javascript-performance/#PageComment_9991 Simon,
There is certainly a potential problem with events taking a while to fire, if you bind too many delegates/on handlers on a top-level element like "body". Doing that would mean that every event has to run through many handlers before finding the correct one, thereby slowing event processing. However, in practice, I've never found this to be a problem. I've found start-up time far more problematic than event execution time.

Still, you make a good point, we need to be careful and bind delegate/on events to as specific elements in the DOM as possible. That mitigates the potential problem of slow event firing. So, instead of binding to "body", you would bind to "#navigation", as an example.

Matt,
You are totally correct that delegation has been part of jQuery for a long time. However, in 1.7, with the new "on" method, it has become the recommend default way of binding any event. The jQuery team substantially improved delegate performance in the 1.7 version. See this blog post:
http://blog.jquery.com/2011/11/03/jquery-1-7-released/

So, while you could write delegates before 1.7, they weren't appropriate in every situation. Now, however, you can do so as the default. The new "on" method is always the right choice :)

Happy Javascripting,
Julian Mon, 18 Jun 2012 11:10:17 +1200 Julian Seidenberg http://www.silverstripe.org/javascript-performance/#PageComment_9991 http://www.silverstripe.org/javascript-performance/#PageComment_9986 I noticed that these tests only consider startup time. Have you tested the relative performance of the events actually firing compared to how they're added? Thu, 14 Jun 2012 19:31:14 +1200 Simon http://www.silverstripe.org/javascript-performance/#PageComment_9986 http://www.silverstripe.org/javascript-performance/#PageComment_9984 Actually, regarding #7, proper event delegation in jQuery has been around since 1.4.2 (http://api.jquery.com/delegate/). I say "proper" because there technically was event delegation since 1.3 but it hadn't found its true name yet (http://api.jquery.com/live/) Thu, 14 Jun 2012 14:03:33 +1200 Matt http://www.silverstripe.org/javascript-performance/#PageComment_9984