Syntax for accessing controls from javascript using variable names

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John Holmes - 10 Mar 2004 17:29 GMT

I'd like to use a generic validation function that I pass the control name
to and have an alert box come up and then select the text in the text box
and return the focus to the textbox if not valid. It's not working correctly
and I expect my syntax isn't quite right. Please check it out and let me
know what I'm doing wrong. Thanks, John Holmes

function validateNumeric(control)

{

if(isNaN('document.Form1.'+control+'.value'))

{

alert('This field represents a money value and must be numeric.');

'document.Form1.'+control+'.focus()';

'document.Form1.'+control+'.select()';

}

}

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gilly3 - 10 Mar 2004 17:41 GMT

> I'd like to use a generic validation function that I pass the control
> name to and have an alert box come up and then select the text in the
> text box and return the focus to the textbox if not valid. It's not
> working correctly and I expect my syntax isn't quite right. Please
> check it out and let me know what I'm doing wrong. Thanks, John Holmes

You have your object reference in quotes - this is incorrect. isNaN is
evaluating a string instead of the value of your control.

If you are passing in a string for control, construct your object
reference like this:

document.forms["Form1"].elements["control"]

I'd plop that object reference in a variable and code your function like
this:

function validateNumeric(control)
{
var oControl = document.forms["Form1"].elements["control"];
if(isNaN(oControl.value))
{
alert("This field represents a money value and must be numeric.");
oControl.focus();
oControl.select();
}
}

good luck

-ivan.

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John Holmes - 10 Mar 2004 18:37 GMT

This looks like it should work except for the quotes around the passed
parameter variable "control", won't it take that as a string literal and not
a variable?

I've tried without the quotes and with the quotes and I continue to get
errors. I am confused on how to reference variables correctly in this model.
Thanks, john

> > I'd like to use a generic validation function that I pass the control
> > name to and have an alert box come up and then select the text in the
[quoted text clipped - 27 lines]
>
> -ivan.

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gilly3 - 10 Mar 2004 18:49 GMT

> This looks like it should work except for the quotes around the passed
> parameter variable "control", won't it take that as a string literal
[quoted text clipped - 3 lines]
> get errors. I am confused on how to reference variables correctly in
> this model. Thanks, john

Whoops! Heh. Good catch. Yes, that should be

document.forms["Form1"].elements[control]

You say you've tried it like that and still are having trouble? The
control parameter should be a string (literal or variable) that contains
the name of the form element you want to validate. So, this should work
with your function:

<form name="Form1">
<input name="Field1">
<button onclick="validateNumeric('Field1');">Validate</button>
</form>

-ivan.

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bruce barker - 12 Mar 2004 01:48 GMT

its simpler and cleaner if you just pass the control:

<form name="Form1">
<input name="Field1">
<button onclick="validateNumeric(this);">Validate</button>
</form>

<script>
function validateNumeric(oControl)
{
if(isNaN(oControl.value))
{
alert("This field represents a money value and must be numeric.");
oControl.focus();
oControl.select();
}
}
</script>

-- bruce (sqlwork.com)

> > This looks like it should work except for the quotes around the passed
> > parameter variable "control", won't it take that as a string literal
[quoted text clipped - 19 lines]
>
> -ivan.

Reply to this Message

Randy Webb - 12 Mar 2004 05:25 GMT

> its simpler and cleaner if you just pass the control:
>
[quoted text clipped - 14 lines]
> }
> </script>

"this", in that context, refers to the button, not the input. So the
function is checking to see if the buttons value is a number, if its not
then you get the alert.

Signature

Randy
Chance Favors The Prepared Mind
comp.lang.javascript FAQ - http://jibbering.com/faq/

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bruce barker - 12 Mar 2004 17:24 GMT

you're right, i should have looked what the code was doing closer. a more
common approach whould be:

<form name="Form1">
<input name="Field1" onblur="validateNumeric(this);">
</form>

<script>
function validateNumeric(oControl)
{
if(isNaN(oControl.value))
{
alert("This field represents a money value and must be numeric.");
oControl.focus();
oControl.select();
}
}
</script>

-- bruce (sqlwork.com)

> > its simpler and cleaner if you just pass the control:
> >
[quoted text clipped - 23 lines]
> Chance Favors The Prepared Mind
> comp.lang.javascript FAQ - http://jibbering.com/faq/

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Dave Anderson - 12 Mar 2004 18:20 GMT

> its simpler and cleaner if you just pass the control:
>
> <form name="Form1">
> <input name="Field1">
> <button onclick="validateNumeric(this);">Validate</button>
> </form>

An alternative correction to "this" example:

<BUTTON ONCLICK="validateNumeric(this.form.Field1)" ...

Signature

Dave Anderson

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Syntax for accessing controls from javascript using variable names

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