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Question

Error when trying to refer to a field by name

Answer 1

+2 A:

In your javascript you have referred to the form as 'my_formm' i.e. you have an extra 'm' at the end which is not present in the HTML, this could be your problem.

murdoch 2010-06-09 15:52:18

thats y i passing the form name as parameter in the check_length() method

raja 2010-06-09 15:54:48

but you are not referencing to the variable passed into the function because you have placed 'document.' in front of my_formm, also, you pass the parameter in as a string not the form its self, you want to remove 'document.' and change your method call to onchange="check_length(this,"my_text")"

murdoch 2010-06-09 15:59:29

is it possible by passing form name instead of this?

raja 2010-06-09 16:02:18

Yes but there isn't any need as 'this' already refers to the form you need, if you must could give the form an id instead of a name then inside your function call 'document.getElementByID(my_formm)'

murdoch 2010-06-09 16:10:50

Answer 2

A:

Just do onChange=check_length(this)

and in your function

function check_length(element)
     {
       // element points to the element in question
       // element.form points to the form if you need it
       alert(element.value); 
     }

Gaby 2010-06-09 15:53:13

My requirement is need to pass the form name and field name not using this.. Using that i should do the validation

raja 2010-06-09 16:00:58

@raja, you can get those from the element... `element.form.name` and `element.name`.

Gaby 2010-06-09 16:11:28

Answer 3

+6 A:

Your check_length function is using variables to identify the form and field names, however, by using dot notation, you are referring to a element of document named my_formm. When you are are using variable names, you should use the bracket notation instead:

function check_length(my_formm,fieldName)
{
  alert(fieldName); 
  alert(document[my_formm][fieldName].value); 
}

Also, you should really quote attributes in your input:

<input type="text" onKeyPress="checkCompanyName();" onChange="check_length('my_form', 'my_text');" name="my_text" rows="4" cols="30" value="">

Daniel Vandersluis 2010-06-09 15:53:16

+1 Much more succinct than my answer. Deleting mine.

Vivin Paliath 2010-06-09 16:10:29

The standard way (DOM0) to access forms and form elements is: `document.forms[my_formm].elements[fieldName]`

CMS 2010-06-09 16:23:14

Answer 4

+1 A:

Why does your JavaScript method take in that first parameter if it never uses it?

JB King 2010-06-09 15:54:39

Answer 5

A:

In general it would be nice to write WHAT error are you getting...

anyhow checkCompanyName is not defined in the code you wrote.

Also you're passing two strings as variable, they do not have properties...

A better way to do this:

<script type="text/javascript">
function checkLength()
    {
    inp = document.getElementById("myInput");
    len = document.getElementById("len");
    len.value = inp.value.length;
    }
</script>

<input id="myInput" onkeyup="checkLength()" />
<input id="len" />

EDIT AFTER COMMENT:

<script type="text/javascript">
function checkLength(inputname, lenname)
    {
    inp = document.getElementById(inputname);
    len = document.getElementById(lenname);
    len.value = inp.value.length;
    }
</script>

<input id="myInput" onkeyup="checkLength('myInput', 'len')" />
<input id="len" />

nico 2010-06-09 15:56:50

Hi:My requirement is need to pass the form name and field name.. Using that i should do the validation

raja 2010-06-09 16:00:03

@raja: see my edited answer

nico 2010-06-09 16:04:30

Answer 6

A:

document.my_formm looks for a form named my_formm. You need to use the associative array sintax instead, like document[my_formm], which will pass the value in my_formm at runtime, rather than looking for a property in the document object called my_formm (which doesn't exist).

jasongetsdown 2010-06-09 16:07:31

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Error when trying to refer to a field by name

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