Random Banner Null object problem...ongoing...help please!! :(

[flipside1212]

Hi. I'm having a problem with my random ad banner. It keeps giving the error "BannerAdImages[..].src is null or not an object" It happens a minute or two after each page loads and on different images. Here is the code:

<SCRIPT LANGUAGE=&quot;javascript&quot;><!--

var ImageFolder = &quot;

http://www.dreameyes.com/ads/&quot;;

//Folder name containing the images
var ImageFileNames = new Array('ad1_beatstreet_small.jpg', 'ad2_zionsgate_small.jpg', 'ad3_brina_small.jpg', 'ad4_metro3106_small.jpg', 'ad5_eightzero_small.jpg', 'ad6_dadabase_small.jpg', 'ad7_karmajeans_small.jpg', 'ad9_blueskies_small.jpg', 'ad10_bcalhoun_small.jpg');
var ImageURLs = new Array('

http://www.beatstreet.ca',

'

http://www.zionsgate.com',

'

http://www.duringtheday.com',

'

http://www.metro3106.com',

'

http://www.eightzero.net',

'

http://www.dadabase.ca',

'

http://www.karmajeans.com',

'

http://www.blueskiesanddaisies.com',

'

http://www.bcalhounphoto.com');

var DefaultURL = '

http://www.dreameyes.com';

var DisplayInterval = 7;
var TargetFrame = &quot;&quot;;
var IsValidBrowser = false;
var BannerAdCode = 0;
var BannerAdImages = new Array(NumberOfImages);
var DisplayInterval = DisplayInterval * 1000;
var NumberOfImages = ImageFileNames.length;

if (ImageFolder.substr(ImageFolder.length - 1, ImageFolder.length) != &quot;/&quot; && ImageFolder != &quot;&quot { ImageFolder += &quot;/&quot;;
}

if (TargetFrame == '') {
var FramesObject = null;
} else {
var FramesObject = eval('parent.' + TargetFrame);
}

function InitialiseBannerAdRotator() {

var BrowserType = navigator.appName;
var BrowserVersion = parseInt(navigator.appVersion);

if (BrowserType == &quot;Netscape&quot; && (BrowserVersion >= 3)) {
IsValidBrowser = true;
}

if (BrowserType == &quot;Microsoft Internet Explorer&quot; && (BrowserVersion >= 4)) {
IsValidBrowser = true;
}

if (IsValidBrowser) {
TimerObject = setTimeout(&quot;ChangeImage()&quot;, DisplayInterval);
BannerAdCode = 0;

for (i = 0; i < NumberOfImages; i++) {
BannerAdImages = new Image();
BannerAdImages.src = ' ' + ImageFolder + ImageFileNames;
}
}
}

function ChangeImage() {

BannerAdCode = (Math.round((Math.random()*8)+1));
window.document.bannerad.src = BannerAdImages[BannerAdCode].src;
TimerObject = setTimeout(&quot;ChangeImage()&quot;, DisplayInterval);
}

function ChangePage() {

if (IsValidBrowser) {window.open(ImageURLs[BannerAdCode]);}
else if (!IsValidBrowser) {document.location = DefaultURL;}

}

// --></script>

<A HREF=&quot;javascript:ChangePage()&quot;><img src=&quot;ads/ad1_beatstreet_small.jpg&quot; alt=&quot;Banner Advertisement&quot; border=&quot;0&quot; hspace=&quot;0&quot; name=&quot;bannerad&quot; WIDTH=&quot;230&quot; HEIGHT=&quot;85&quot;></a>

************Your help is greatly appreciated!!!!

 

[dwarfthrower]

[tt]BannerAdCode = (Math.round((Math.random()*8)+1));[/tt]

Will assign a number from one to eight (inclusive) to the [tt]BannerAdCode[/tt] variable.

However, arrays in Javascript start at index 0. Whenever [tt]BannerAdCode[/tt] gets assigned a '7' or '8' your code looks for the image URL at the eighth or ninth position in the array (which are both blank), hence the error.

Change the random number generator to:
[tt]BannerAdCode = (Math.round(Math.random()*7));[/tt]

Which will return a number between zero and six (inclusive), more closely matching the range of index values in your array.

 

[dwarfthrower]

Eh, sorry, didn't count the full number of elements in your array...

The other problem is that you set the length of the BannerAdImages to NumberOfImages before you assign a value to the NumberOfImages variable as so:
[tt]
var BannerAdImages = new Array(NumberOfImages);
var DisplayInterval = DisplayInterval * 1000;
var NumberOfImages = ImageFileNames.length;
[/tt]

This is not a huge problem as you add the elements to the array later.

However, as I stated (incorectly) before [tt]BannerAdCode = (Math.round((Math.random()*8)+1));[/tt] will return either 1, 2, 3, 4, 5, 6, 7, 8, or 9.

It will be that 9 causing the problem - 9 referring to the empty tenth spot in the array.

May I suggest an even better approach:
[tt]BannerAdCode = (Math.floor(Math.random()*NumberOfImages));[/tt]

Which will return anything from zero up to however many images are in the array.

 

[flipside1212]

thank you so much, you are a genius. Saved me hours of trial and error bullcrap. Thanks once again!!!