Error in form validation using "this" keyword

danielh · January 10th, 2004, 07:40 PM

Greetings,

I am having a yuk debugging problem. My ego is deflated.

I am trying to pass variables into a validation function (client-side) from multiple locations in my web site, so I want to use the "this" keyword from each form.

I have condensed the code into as small a chunk as possible as follows. (The loose doctype was a desperate gasp.):

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TRhtml4/loose.dtd">
<html>
<head>
<title>Untitled Document</title>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">

<script language="JavaScript" type="text/javascript">

function validateitem(objForm){
    returnValue=false;
    document.write("form element 'amount': " +objForm.amount.value+ "<br>\r");
    document.write("form element 'item_name': " +objForm.item_name.value+ "<br>\r");
    document.write("form element 'business': " +objForm.business.value+ "<br>\r");
    return returnValue;
    }
</script>

</head>
<body>

<form name="form1"
action="https://www.paypal.com/cgi-bin/webscr"
method="post"
onsubmit="return validateitem(this);">
<input type=hidden name="cmd" value="_cart">
<input type=hidden name="business" value="[email protected]">
<input type=hidden name="item_name" value="Bulgarian Lavender">
<input type=hidden name="amount" value="12">
<input type=submit name="submit" value="Submit" alt="Make payments with PayPal - it's fast, free and secure!">
</form>
</body>
</html>

Pressing the submit button produces the following error:

"'item_name.value' is null or not an object."

If I delete the .value as follows:

objForm.amount
objForm.item_name

then these values are returned as "undefined."

Ironically, If I switch the order of statements in the function as follows:

function validateitem(objForm){
    returnValue=false;
    document.write("form element 'item_name': " +objForm.item_name.value+ "<br>\r");
    document.write("form element 'amount': " +objForm.amount.value+ "<br>\r");
    document.write("form element 'business': " +objForm.business.value+ "<br>\r");
    return returnValue;
    }

then whichever write statement is written first, will correctly execute with the correct output, and the latter statements will be undefined.

Thank you very much for your time.
Daniel Hutchins

Thank you,
Daniel Hutchins
Woodbridge, CA
http://www.finehomemadesoap.com

Snib · January 10th, 2004, 07:49 PM

Daniel,

I think that you must assign IDs to the inputs that you refer to. However, perhaps this is not the problem, having the first one in the list work fine.

Maybe you should try:

<input type=hidden id="item_name">

etc.

Sorry if this isn't the problem, just a guess.

Snib

danielh · January 10th, 2004, 11:12 PM

Thank you Snib, but guess what....

Using id="item_name" I still get the error message "'item_name.value' is null or not an object."

Everybody passes variables into a validation function. There has got to be a simple mistake in here somewhere.

Further debugging information: I used typeof(objForm) to make sure it is an object (hopefully the forms object) and objForm.elements.length

to determine how many elements it has. The code acknowledges that I have an object, but with zero elements. The output (which is written

before the error message) is as follows:

type: object
number of elements: 0
name of form: form1
[followed by the error message "'item_name.value' is null or not an object."]

for the following code:

function validateitem(objForm){
    var returnValue=false;

    var x;

    x = typeof(objForm);
    document.write("type: " +x+ "<br>\r");

    x = objForm.elements.length;
    document.write("number of elements: " +x+ "<br>\r");

    x = objForm.name;
    document.write("name of form: " +x+ "<br>\r");

    x = objForm.item_name.value;
    document.write("form element item_name: " +x+ "<br>\r");

    return returnValue;
}
</script>

<form action="https://www.paypal.com/cgi-bin/webscr"
        name="form1"
        method="post"
        onsubmit="return validateitem(this)">
    <input type=hidden id="item_name" name="item_name" value="Bulgarian Lavender">
</form>

I have tried passing the form using onsubmit="return validateitem(document.form1)", and I still got the same problem in the validation

function.

Thank you,
Daniel Hutchins
Woodbridge, CA
http://www.finehomemadesoap.com

joefawcett · January 11th, 2004, 02:56 PM

I can't see anything obvious. One thing though is to rename your submit button to something other than 'submit'. You are confusing the issue because form.submit method is now over-ridden by form.submit element.

--

Joe

pgtips · January 12th, 2004, 08:22 AM

Its just the use of document.write that's causing the problems. As soon as you do a document.write you're clearing out the existing document, so the form values are no longer valid. Change each document.write to an alert and you'll see it works just fine.

Snib · January 12th, 2004, 06:22 PM

That explains why only the first line works. After the first line, the others no longer exist.

Snib

danielh · January 19th, 2004, 03:39 PM

Solution to my own topic:

Everything was correct...except I ruined everything when I used "document.write()" in debugging.

Indeed document.write() did write to the current page, after erasing all data that was on it, including the form object.

Wow did I feel ridiculous when I discovered this truth. Oops.

regards,

Thank you,
Daniel Hutchins
Woodbridge, CA
http://www.finehomemadesoap.com

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thanks
barry
[email protected]

ezhost · June 2nd, 2004, 05:00 PM

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