Topic awaiting preservation: I *know* it's null.. that's why I asked! (Page 1 of 1)

I've I isolated the following problem:

if (photoS[st2].src){

  timer = setTimeout("blah(blah,st2)",50);

}

the problem is that if (photoS[st2].src) part...

I eventually get a 'photoS[...].src' is null or not an object error. I increment st2 and I expect that eventually photoS[st2].src will be null-- that's why the if() statement is there!

I'd like it to run thru the values and when 'photoS[st2].src' is null just don't run the if(). What am I doing wrong?


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try this:

if (photoS[st2] && photoS[st2].src){
timer = setTimeout("blah(blah,st2)",50);
}

Yeah. See, you're allowed to check if something is undefined, but if you try to use an undefined thing as if it were an *object*, then the browser will complain.

So if

myobject is defined, but
myobject.myproperty is *not* defined, then

if (myobject) {...} will evaluate to true,
if (myobject.myproperty) {...} will evaluate to false, and
if (myobject.myproperty.anotherproperty) {...} will cause an error.

So you have to test each "level" down from the top level object, as lallous said.

If there's a chance that photos itself won't be defined, then you'll have to say:

if (photoS && photoS[st2] && photoS[st2].src) {...} // test each level down from the top, in descending order.

This ensures that each object is defined before you try to test its children.

BTW: did you mean to spell "photos" "photoS"? That might be the problem.

ok, I tried it, and it didn't work...

I suspect that adding that fix just makes the if() true all the time because it just ends up crashing on the image change part the next time it rolls (seeing as photoS[ANY NUMBER NON-NEGATIVE NUMBER] will always be valid- that's what I think, anyway..)

I posted it here: http://www.twistedport.com/misc/test/imgani.html

*sigh* I am all outta ideas. I tried your ideas and even some funky shit I came up with, but nothing worked..

*head on over to jskit*


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[This message has been edited by Petskull (edited 09-12-2002).]

ok, new idea... maybe I should just code the upper and lower limits as global variables... it's ugly, though...

any other way?



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I'm not getting any errors. I don't see what's wrong. What is it doing wrong? What is it *supposed* to do?

oh, my bad....

it's supposed to rollover three images- up and down- onmouseover (it's that image above 'Notes')

(I just added the images)

you get an error after the images reach the top...

...it's because of the 'if()' statement...


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Could you remove the alert boxes? I think they're making it behave differently for me so I'm not getting the error.

there... sorry, I was testing..

Fuck, don't tell me this it just an IE6.0 bullshit...


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[This message has been edited by Petskull (edited 09-13-2002).]

hi PS,

if you apply the patch as i told you, you would avoid the first problem...but it seems you're not doing error checks in the rest of your code too!

when 'st2' (as an array index) is bigger than photoS.length you're getting this error!

you have this error at this line too:
document.images[set].src = photoS[start].src;
// window.status = set + start;
etc...

dunno what you're trying to do, but consider changing the method.

yeah, I decided last night- in a fit of smokey rage- that what I'm going to do is just call one function, which would put the parameters into hard variables, and I'm just gonna use the values from the hard data for the 'aniup' function...

it's ugly, but it'll work...


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Hmm... still couldn't get an error =)

Slime, you know how to reproduce the error?

I hovered over the image @ the bottom a couple of times so I get the error.

Oh, shoot, I forgot that ever since I installed VC++ it screws up error messages so I don't get them. Quite an annoyance. I used the workaround I've found and got the error =)

Petskull:

This should fix it. "Start" is eventually becoming equal to 2, which makes st2 equal to 3, and there is no third element in the array. If I understand your function right, you want to say

if (st2 < 3){

for the first if, and

if (st2 >= 0) {

for the second if.

In addition, inside the if(special == 'rev'), you don't want to use the st2 variable directly, since you know it's equal to 3. Instead, use st2-1:

timer = setTimeout("aniup(theset," + (st2-1) + ",endup,'dn',special)",50);

Actually, that line won't work at all. Remember that variables like special, endup, and theset are only defined within this function; when this function exits, and later the function you create with setTimeout is called, they won't exist anymore. So you must use:

timer = setTimeout("aniup("+theset+"," + (st2-1) + ","+endup?+",'dn',"+special+")",50);

Then it should, in theory, work.

Oh, one more thing. I see you using

if (...){...}
else {
if (...) {...}
}

Where you can just use

if (...) {...}
else if (...) {...}

They are actually the same thing, it's just that the second drops a pair of brackets that aren't necessary. However, lots of people tend to think of "if", "else if", and "else" as three separate things, which is also fine. Think of it however you want, you just don't need those brackets after the else =)

yeah, I noticed that I was trying to use the dimentions of the array as the start-stop delimiter..

...then last night I think, "Why the fuck would I want to do that?"

I'm going to go with the plan of calling a function first to memorize all the initial parameters and THEN running the funtion with the timeout loop.

btw, I used those embedded 'if' statement because I forgot that 'else if' in Javascript was 'else if'- I'm still running off of the Perl convention of 'elsif'. When it didn't work, I just got rid of it and figured I'd ask later...




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ok, I got it working fine..

Now this is funny inquiry:

I have this line:

document.images[set].src = photoS[start].src;

now, I still want to use the array 'photoS[]', but I want to make it's name dynamic...

for example:

var myarray = "photoS"
document.images[set].src = myarray[start].src;


What's the way to do this? (I know that doesn't work... I tried it)


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got it with this..

eval("document.images[set].src = "+set+"S["+start+"].src;");

this the proper way?


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Ew, eval is ugly and slow. (Though heavily used for such things, so don't feel bad.) Make use of the window object:

var myarray = "photoS"
document.images[set].src = window[myarray][start].src;

the Window object is the "top level" object that contains all global variables and objects - including a reference to itself, which you can access via "window" or "self" as I did here. =)

http://www.twistedport.com/misc/test/imgani.html

check it out now... it's almost done...
...all that's left is to dynamicize the framerate via an array...


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Great... now this line doesn't work...

superpic = initParam[0];
superset = initParam[1];
document.images[superpic].src = window[superset][0].src;

it's inside a function... is that a problem?


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Well, are superpic and superset defined either within the function or as global variables? If not, then they either need to be global variables (by saying var superpic, superset outside any functions), or they need to be passed to the function as arguments.

Making them global variables could cause issues (since they don't return to undefined every time the function they're defined in is called), so try passing them to the function.

I was stupid... I was using variables that I hadn't run yet...
I completed it.... lookie here:
http://www.ozoneasylum.com/Forum2/HTML/001773.html


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