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Thread: Undefined Array Problem

  1. #1
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    Default Undefined Array Problem

    Hi,
    I'm new to java and have a small but annoying problem with an array. The script rotates a randomly selected banner from an array and changes the banner every few seconds. The problem is that when the page is first loaded the word 'undefined' displays next to the first banner. When the second banner is displayed everything works fine.

    Here is the function I am using

    function randomBanner() 
    { 
     
    var myBanners=new Array(3); 
    var i = Math.floor(Math.random() * 3); 
     
     
    myBanners[0]="image 1"; 
    myBanners[1]="image 2"; 
    myBanners[2]="image 3"; 
     
     
    document.getElementById('banners').innerHTML = myBanners[i]; 
     
    setTimeout("randomBanner()",5000 );//5000 = 5 seconds 
     
    }
    and here is the html code

    HTML Code:
    <head> 
    <script type="text/javascript" src="rotator.js"></script> 
    </head> 
    
    <body> 
    <div id="banners"> 
    <script type="text/javascript">document.write(randomBanner());</script> 
    </div> 
    </body> 
    I have tried declaring the variables and even the array itself outside the function to no avail. I have set up a test page so you can view the problem here

    Please can someone help?
    Last edited by helloworld922; April 13th, 2011 at 09:58 AM.


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    Super Moderator helloworld922's Avatar
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    Default Re: Undefined Array Problem

    Sorry, but that's javascript code, not Java code. While the two may look similar, they are in fact quite different. I've moved this to the Other Programming Languages forum on the off-chance that someone here knows Javascript, but you may want to consider finding a Javascript forum to ask you question on as they'd be better suited to answer your question.

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    Super Moderator Json's Avatar
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    Default Re: Undefined Array Problem

    Hello,

    The reason it prints out undefined is because you try to print whatever the randomBanner() method returns which is nothing or undefined.

    You need to change your HTML slightly to this:

    HTML Code:
    <head> 
    <script type="text/javascript" src="rotator.js"></script> 
    </head> 
    
    <body> 
    <div id="banners"> 
    <script type="text/javascript">randomBanner();</script> 
    </div> 
    </body>
    See how the document.write has been removed since we don't need to print the output of the method because the method will change the innerHTML of that div anyway.

    // Json

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    JavaPF (April 18th, 2011)

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