Problem trapping nulls in onload script.

termid0g3 · Jun 28, 2004

I have the following tidbit of script that runs in the body onload of an ASP.NET page.

Document.forms errors out every time ctl is null or blank:

document.forms(...).elements(...) could not be found

Am I doing something wrong syntactically?

Thank you!!
Paul

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" >
<html>
<head>
<title>Status Tracker</title>
<link href="styles.css" type="text/css" rel="stylesheet" />
<script language="javascript">
function setFocus()
{
ctl = "<%= controlToFocus %>";
if (ctl != "") {
if (ctl != null) {
document.forms("TimeEntry").elements(ctl).focus();
}
}
}
</script>
</head>
<body onload="setFocus();">

LFI · Jun 28, 2004

My interpretation of the error message you're getting is that it can't find the element you're requesting to send focus to.

Add an alert to display the value of ctl after you assign it <%= controlToFocus %>. Make sure this value is actually one of the form elements (by NAME).

'hope that helps.

--Dave

BillyRayPreachersSon · Jun 28, 2004

You're using incorrect syntax to access your form elements. Replace the round brackets with square brackets... So this:

Code:

document.forms("TimeEntry").elements(ctl).focus();

becomes this:

Code:

document.forms["TimeEntry"].elements[ctl].focus();

Hope this helps,
Dan

BillyRayPreachersSon · Jun 28, 2004

You can also replace this:

Code:

if (ctl != "") {
            if (ctl != null) {

with this:

Code:

if (ctl != '' && ctl != null) {

Dan

LFI · Jun 28, 2004

Dan,

I thought it might be a square-bracket problem also, but if that were the case, I think the error message would have flagged document.forms(...) as being in error, before it even got to document.forms(...).elements(...).

So I tried this experiment:

Code:

<html>
<head>
<script>
function displayText()
{
 [b]//note the use of parentheses[/b]
 alert(document.forms('form1').elements('text1').value);
}
</script>
</head>
<body>
<form name='form1'>
<input type='text' size='30' name='text1' />
<input type='button' value='display text' onclick='displayText()' />
</form>
</body>
</html>

When I type something in the text field and press the button, the script correctly finds the value.

I tried it by using indexes as well:

document.forms(0).elements(0).value

...and it still works.

This is only IE6 that I've tried this in and perhaps the parentheses don't have cross-browser appeal, but I think termid0g3's error message would be more like 'Object expected' if it didn't recognize the parentheses.

--Dave

termid0g3 · Jun 28, 2004

Okay, I solved the problem. CTL is assigned a value in the datagrid prerender and it's NEVER blank or null.

I added a length check to CTL (if ctl.length > 9) and tested again. It works perfectly.

Thanks to everyone for all of your help.
Paul

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Problem trapping nulls in onload script.

termid0g3

MIS

LFI

Programmer

BillyRayPreachersSon

Programmer

BillyRayPreachersSon

Programmer

LFI

Programmer

termid0g3

MIS

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