var for form element name

[dstefani]

Hello,

I'm trying to pass a var to a function for it to be used as the name of
a form element.

IE:

function doThis(form, elemName) {

if( form.elemName.v alue == false ) {
// do something
}

}

I can't seem to figure out how to use the var where the name goes.

Thanks,

- D

[bobzimuta]

Re: var for form element name

i was able to use
function doThis(formName , elemName) {

if( document.forms[formName].elemName.value == false ) {
// do something
}

}

[Thomas 'PointedEars' Lahn]

Re: var for form element name

dstefani wrote:
[color=blue]
> I'm trying to pass a var to a function for it to be used as the name of
> a form element.
>
> IE:[/color]

The user agent does not matter, this feature is supported by all JS-capable
HTML UAs (part of the so-called DOM Level 0).
[color=blue]
> function doThis(form, elemName) {
>
> if( form.elemName.v alue == false ) {[/color]

Use bracket property accessor syntax to access an element of the collection:

if (form.elements[elemName].value)
{

Since the `value' property of objects referring to form controls is of type
string, it can never be `false'. You could test for the empty string (x ==
'' or x.length == 0), or you could just use automatic type conversion as I
did.
[color=blue]
> // do something
> }
>
> }
>
> I can't seem to figure out how to use the var where the name goes.[/color]

<http://jibbering.com/faq/#FAQ4_13>


HTH

PointedEars

[dstefani]

Re: var for form element name

Excellent, thanks.

I haven't had to do any JS stuff in a while. Serious cobwebs!

Thanks,

- D

[Thomas 'PointedEars' Lahn]

Re: var for form element name

Thomas 'PointedEars' Lahn wrote:
[color=blue]
> dstefani wrote:[color=green]
>> function doThis(form, elemName) {
>>
>> if( form.elemName.v alue == false ) {[/color]
>
> Use bracket property accessor syntax to access an element of the
> collection:
>
> if (form.elements[elemName].value)
> {[/color]

Additional note: Since I do not know which value you are passing for `form',
I have to consider that it may be a number or string identifying the form
element by its index, name or ID, instead of a reference to a
HTMLFormElement object. In this case, you would need

if (document.forms[form].elements[elemName].value ...)
{
// ...
}


PointedEars

P.S.: Please quote what you are replying to, see
<http://jibbering.com/faq/>.

[dstefani]

Re: var for form element name

Well the above works, but now I'm trying to go back and focus on the
errant field, like so:

<code>

if ( TE_digit(form.e lements[elemName].value) == false) {
alert("Yatta, yatta, yatta");
var elem = form.elements[elemName];
elem.focus();
return false;
}
</code>

It still won't focus back on the field that it tested.

What am I missing?

Thanks

- D

[Thomas 'PointedEars' Lahn]

Re: var for form element name

dstefani wrote:
[color=blue]
> Well the above works,[/color]

Which "above" are you talking about?
<http://www.jibbering.c om/faq/faq_notes/pots1.html#ps1P ost>
[color=blue]
> but now I'm trying to go back and focus on the
> errant field, like so:
>
> <code>
>
> if ( TE_digit(form.e lements[elemName].value) == false) {
> alert("Yatta, yatta, yatta");
> var elem = form.elements[elemName];
> elem.focus();
> return false;
> }
> </code>
>
> It still won't focus back on the field that it tested.[/color]

Probably there is more than one form control with that name in
which case all so-named form controls are members of a collection
returned by form.elements[elemName]. The JavaScript console should
show an script error or Exception on the elem.focus() line then.

Otherwise you will have to show more code, best by posting a public
URI for your HTML document.


PointedEars