On Thu, 04 Jun 2009 17:53:31 +0200, Boris Zbarsky <bzbar...@mit.edu> wrote:
João Eiras wrote:
The overhead of comparing the previous with the new value inside the
engine is a fragment of the overhead of calling an ecmascript callback
and doing the same comparison in ecmascript.
For a given operation that has a callback listening, yes. But most
operations do not have a callback listening, as it happens.
You are thinking along the following algorithm
if new_value != old_value then
foreach listener in listeners
call listener
I'm thinking in the following
if has_listeners
if new_value != old_value then
foreach listener in listeners
call listener
So, unless there are listeners (which is a very simple instruction to
evaluate), there is penalty in checking whatever needs to be checked.
And this is what UAs do, considering there is currently a big visible
performance tradeoff when one adds no-op listeners (yes, event
capturing/bubbling also affects it)
--
João Eiras
Core Developer, Opera Software ASA, http://www.opera.com/
