Code Performance Issue

**Richard Cornford** · Jul 20 '05, 02:30 PM

Re: Code Performance Issue

"Martin" <martinorourke1 5@hotmail.com> wrote in message
news:cc11d8c3.0 402130320.7b667 8a1@posting.goo gle.com...
<snip>[color=blue]
> <script>functio n Goodbye()[/color]

Where is your type attribute?
[color=blue]
> {
> for (var i = 0; i <
> document.Defaul tFormName.IgsPe PersonAddrCount ry.length; i++)
> {
> if[/color]
(document.Defau ltFormName.IgsP ePersonAddrCoun try.options[i].value.match(
document.InputF orm.countrycode .value))[color=blue]
> {
> document.Defaul tFormName.IgsPe PersonAddrCount ry.selectedInde x =
> i;
> break;
> }
> }
> }[/color]
<snip>

Resolving absolute property accessors for forms repeatedly will be
relatively time consuming. You should create local variables that refer
to the form object, possibly the select element and certainly the select
element's - options - collection and then make future references to the
properties of those objets relative to the local variable.

var frm = document.forms. DefaultFormName ;
var selectEl = frm.elements.Ig sPePersonAddrCo untry;
var selOptions = selectEl.option s;

var cntryCode = frm.elements.co untrycode.value ;
/* no need to repeatedly look up that string as it
should be constant while the function runs.
*/

Then the number of options is - selOptions.leng th - the option element
at index - c - is - selOptions[c] - and its value is -
selOptions[c].value - and assigning a selected index is -
selectEl.select edIndex = n - . Generally, if you reference the same
object repeatedly with a property accessor in a function you will get
better performance by assigning a reference to that object to a local
variable so that each identifier does not need to be repeatedly
resolved.

After you have done that question the use of the - match - method.
(should it be a comparison? Where failure to equate can be determined
quite quickly. But I have never directly speed tested those two so match
might be quicker, though I doubt it.)

It won't make much difference but you could also loop through the
options collection backwards with:-

for(var c = selOptions.leng th;c--;){

**Bas Cost Budde** · Jul 20 '05, 02:31 PM

Re: Code Performance Issue

Richard Cornford wrote:
[color=blue]
> for(var c = selOptions.leng th;c--;){[/color]

Ah, the old assembler trick. Thanks for showing me, I like that. :-)
[color=blue]
> Incidentally, I use - c - in newsgroup posts because - i - is less easy
> to identify and my word processor likes to capitalise it.[/color]

Food for thought. For non-native english people (like me) the danger of
identification is not so present. You have a word processor with a
strong feeling for personality? ;-)
--
Bas Cost Budde

http://www.heuveltop.org/BasCB

but the domain is nl

DU · Jul 20 '05, 02:31 PM

Re: Code Performance Issue

Bas Cost Budde wrote:
[color=blue]
> Richard Cornford wrote:
>[color=green]
>> for(var c = selOptions.leng th;c--;){[/color]
>
>
> Ah, the old assembler trick. Thanks for showing me, I like that. :-)
>[color=green]
>> Incidentally, I use - c - in newsgroup posts because - i - is less easy
>> to identify and my word processor likes to capitalise it.[/color]
>
>
> Food for thought. For non-native english people (like me) the danger of
> identification is not so present. You have a word processor with a
> strong feeling for personality? ;-)[/color]

Another policy is to give fully intuitive, meaningful identifier to such
variable so that the code is much more understandable and, as a side
effect, avoid this readability issue.
E.g.:
for(var CountryIterator = 0; CountryIterator < objSelect.lengt h;
CountryIterator ++)
{...}

DU

Code Performance Issue

Code Performance Issue

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