Hi
Fritz Zaucker wrote:
> Hi Martin,
>
> On Tue, 20 Jan 2009, Martin wrote:
>
>> I think I found it in my source code. It's a shame.
>>
>> What I was doing in my callback function (called from rpc.callAsync) was:
>>
>> for (i=0;i<result.lenght;i++)
>>
>> and it should have been
>>
>> for (var i=0;i<result.lenght;i++)
>>
>> I think I've been rewriting some global variable called "i" (which
>> could've been part of some class definition or something).
Ouch, the "var i" thing was a tough thing to spot i guess. A variable
must have gotten the name "i" in the optimized code, whereas it worked
in the source.
> two comments (unrelated to your error):
>
> - var in JS is working on a function level, NOT on block-level (as e.g. in
> Perl). So in case you have a variable i outside the for loop but inside
> the same function, you'll still overwriting it, even with var in the for
> loop:
>
> function test() {
> var i=5;
>
> for (var i=0; i<10; i++) {
> }
>
> alert('i='+i);
> }
>
> will give i=9
>
> Very ugly indeed.
>
> - Apparently, in JS result.length in your look will be evaluated in every
> iteration. Therefore you should move it outside the loop:
>
> var i;
> var len=result.length;
> for (i=0; i<len; i++) {
> }
For the sake of compactness, you could also write:
for(var i = 0, len = result.length; i < len; i++){
}
Which does exactly the same thing as the method described above.
> There also seem to be other (rather unexpected) issues with loop
> performance, see e.g.
> http://www.webreference.com/programming/optimize/speedup/chap10/3/2.html
>
> Note: I did not benchmark these optimisations myself yet ...
>
> In any case, they probably really matter only for loops with many
> iterations (or ones being called frequently).
>
> Cheers,
> Fritz
>
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