On Fri, 12 Feb 2010 14:13:57 +0100, Maciej Stachowiak <m...@apple.com>
wrote:
On Feb 12, 2010, at 5:05 AM, Anne van Kesteren wrote:
Is it really a lot of performance? Our developers are not that
convinced.
A patch that made the change in WebKit was measured as a 20% speedup on
the Dromaeo DOM Core tests in both Safari and Chrome. Calling these
query methods is only a small fraction of the test, so this implies a
much larger speedup to the case where getElementsBy* is called in a
loop. Note also that this involved two different JavaScript engines so
it's unlikely to be a quirk specific to one engine. The Gecko bug cited
above also shows dramatic speedups on various tests.
It would be interesting to know what exactly that test is. Optimizing for
benchmarks is not always useful :-)
Also, what happens with garbage collection? Say some isolated piece of
code does:
x = document.getElementsByTagName("x")
x.p = 2
... and then later on some other piece of code does:
y = document.getElementsByTagName("x")
w("p" in y)
Depending on whether or not x got garbage collected you would get a
different result.
--
Anne van Kesteren
http://annevankesteren.nl/
