Help accessing specific nodes

jshl_wiz · June 28th, 2005, 12:55 PM

I'm currently reading the "[u]Professional JavaScript for Web Developers</u>" book by Nicholas C Zakas. In page 171 he talks about how to access specific nodes (he is talking about the DOM) and he shows a way on how to get to them using the tag name. Anyway, this is the code that I'm having trouble with:

Code:

<html>
    <head>
        <title>DOM Example</title>
        <script>
        //<![CDATA[
        var oPs = document.getElementsByTagName("p");
        var oImgsInP = oPs[0].getElementsByTagName("img");
        //]]>
        </script>
    </head>
    <body>
        <p style="color:red" id="p1">
        <img src="images/donramon.jpg" name="something" />

        </p>
        <input type="button" value="show the tag" />
    </body>
</html>

I keep getting the "oPs.1 is null or not an object" and I am copying the code exactly as it is in the book, can anyone help please?

ChrisScott · June 29th, 2005, 04:49 AM

The error is occurring because the script is running before the page is built & the document content therefore is not available.
Try changing the script to...

Code:

window.onload = function(){
    var oPs = document.getElementsByTagName("p");
    var oImgsInP = oPs[0].getElementsByTagName("img");
}

HTH,

Chris

jshl_wiz · June 29th, 2005, 09:45 PM

Thanks, I didn't ever think about that... I'm a JavaScript beginner trying to become a JavaScript Expert so that might have something to do with the problem.:D