popup jscript problem?   

I have the following code to popup a window and set an img's src property:

    <script type="text/javascript">
      function isMethodType(s)
      {
        return (s == "function" || s == "object");
      } 
      var mainPic = document.getElementById("mainPic")
      mainPic.onclick = function () 
      { 
        var winref = window.open("../popup.htm", "popup", 
"width=600,height=500,toolbar=0,resizable=0") 
        if (winref && isMethodType(typeof winref.focus))
        {
          winref.document.getElementById("mainPic").src = mainPic.src
          winref.focus();
        } 
      }
  </script>
</body>

However, I found that sometime it works, but sometime it doesn't work with 
error: "Error: 'document.getElementById(...)' is null or not an object" 
on the line: winref.document.getElementById("mainPic").src = mainPic.src

Did I missed anystep? 

Thanks,

date: Sun, 9 Oct 2005 02:02:04 -0700   author:   nick

Re: popup jscript problem?   

"nick"  wrote in message
news:A6DB6749-C451-48FF-9F06-21D327CE3D76@microsoft.com
> I have the following code to popup a window and set an img's src
> property:
>        var winref = window.open("../popup.htm", "popup",
> "width=600,height=500,toolbar=0,resizable=0")
>        if (winref && isMethodType(typeof winref.focus))
>        {
>          winref.document.getElementById("mainPic").src = mainPic.src
>
> However, I found that sometime it works, but sometime it doesn't work
> with error: "Error: 'document.getElementById(...)' is null or not an
> object" on the line: winref.document.getElementById("mainPic").src =
> mainPic.src

window.open creates a new browser window and initiates navigation, then 
returns. The navigation proceeds asynchronously. So you have a race 
condition: sometimes the popup page finishes loading by the time you 
call getElementById, but other times it is still loading, and the 
mainPic element has not yet been created.

You need to wait until the popup window fires onload event before you 
can access its elements reliably.
-- 
With best wishes,
    Igor Tandetnik

With sufficient thrust, pigs fly just fine. However, this is not 
necessarily a good idea. It is hard to be sure where they are going to 
land, and it could be dangerous sitting under them as they fly 
overhead. -- RFC 1925

date: Sun, 9 Oct 2005 08:42:56 -0400   author:   Igor Tandetnik