RE: Re: which is faster target.getElementsByTagName or target.firstChild / nextSibli

Well, I think the Gecko timing makes sense, but I've no idea what IE thinks
its doing. :)  It is interesting how they execute it differently, but it's
even more interesting how IE is sooo much faster than Gecko.

It is possible that the getElementsByTagName could take longer because it
needs to examine ALL child nodes of the UL, versus the child/sibling option
where only the immediate children are examined.  But I've always thought
that Gecko used more nodes for text than IE...

And to Gerry's point, the child/sibling option would indeed look at all
children, even if they aren't LIs.  But if the markup is good what
childnodes would we expect other than LIs under a UL?  That's not always a
safe presumption, I suppose.

Rebecca, you may want to try Moran's excellent suggestion to iterate through
these 1000 times each and put the timer outside of the iteration.  That'll
magnify the real execution time and hide some of the randomness.

Thanks for reporting your results!

-ryan

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of
becs027
Sent: Thursday, April 06, 2006 7:01 PM
To: [email protected]
Subject: [wdf-dom] Re: which is faster target.getElementsByTagName or
target.firstChild / nextSibli

Thanks. I get weird results, and had to change the timediff bit a
little to get a result, I used:

var nTimeDiff = dEnd.getMilliseconds() - dStart.getMilliseconds();

In Firefox 1.5:
getElementsByTagName took 313ms
firstChild / nextSibling took 516ms

In Internet Explorer 6:
getElementsByTagName took 265ms
firstChild / nextSibling took 156ms

So looks like it depends on the browser. My function is only for IE
which helps :)

Cheers
Rebecca

--- In [email protected], "Ryan Hicks" <ryan.c.hicks@...> wrote:
>
> Rebecca,
> 
>  My vote would likely be for the getElementsByTagName, simply
because the
> conditional in the other option would have to reference the DOM an
> additional time for each iteration.
> 
>  However, votes aside, you can always test the amount of time your code
> takes to execute by doing something like the following:
> 
>  var dStart = new Date();
> 
> 	...chunk of code...
> 
>  var dEnd = new Date();
>  var nTimeDiff = dEnd.getDate() - dStart.getDate();
>  alert('Execution time: ' + nTimeDiff + 'ms');
> 
>  Without having your actual DOM, I can't test these two scenarios to
verify
> if my vote is correct.  If you find that this technique gets you an
answer,
> I'd love to know which version wins out!
> 
> -ryan
> 
> -----Original Message-----
> From: [email protected] [mailto:[email protected]] On
Behalf Of
> becs027
> Sent: Thursday, April 06, 2006 4:44 PM
> To: [email protected]
> Subject: [wdf-dom] which is faster target.getElementsByTagName or
> target.firstChild / nextSibling
> 
> Hi all,
> 
> I'm doing an onload script to add rollover behaviour to list items
> (dropdown menu style) for IE, and want to check which of two ways is
> faster.
> 
> ------------------------------------------------
> 
> Option 1 - add the behaviour using target.getElementsByTagName:
> 
> if (document.getElementById('navigation')) {
> 	    var target = document.getElementById('navigation');
> 	    var targetbuttons = target.getElementsByTagName('li');
> 
> 	    for (var i = 0; i < targetbuttons.length; i++) {
> 		targetbuttons[i].onmouseover = rollover;
> 		targetbuttons[i].onmouseout = rolloff;
>             }
> 	}
> 
> ------------------------------------------------
> 
> Option 2 - add the behaviour with a while loop using firstChild,
> nextSibling:
> 
> if (document.getElementById('navigation')) {
>                 var target = document.getElementById('navigation');
>                 var targetbutton = target.firstChild;
> 
>                 while (targetbutton) {
>                     targetbutton.onmouseover = rollover;
>                     targetbutton.onmouseout = rolloff;
>                     targetbutton = targetbutton.nextSibling;
>                 }
>             }
> 
> ------------------------------------------------
> 
> Thanks :)
> Rebecca
> 
> 
> 
> 
> 
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