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From: FAQ server on 7 Aug 2010 19:00
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FAQ Topic - How do I get the value of a form control?
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In HTML documents, a form may be referred to as a property of the
`document.forms` collection, either by its ordinal index or by name
(if the `form` has a name). A `form`'s controls may be similarly referenced
from its `elements` collection:

var frm = document.forms[0];
var control = frm.elements["elementname"];

Once a reference to a control is obtained, its (string) `value`
property can be read:-

var value = control.value;
value = +control.value; //string to number.

Some exceptions would be:

First Exception: Where the control is a `SELECT` element, and
support for older browsers, such as NN4, is required:

var value = control.options[control.selectedIndex].value;

Second Exception: Where several controls share the same name,
such as radio buttons. These are made available as collections
and require additional handling. For more information, see:-

<URL: http://jibbering.com/faq/notes/form-access/>
Unsafe Names for HTML Form Controls [ref 1]

Third Exception: File inputs. Most current browsers do not allow
reading of `type="file"` input elements in a way that is useful.

References:
-----------

[1] http://jibbering.com/faq/names/


The complete comp.lang.javascript FAQ is at
http://jibbering.com/faq/

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From: Dr J R Stockton on 9 Aug 2010 14:50
In comp.lang.javascript message <4c5de57b$0$280$14726298(a)news.sunsite.dk
>, Sat, 7 Aug 2010 23:00:03, FAQ server <javascript(a)dotinternet.be>
posted:

>FAQ Topic - How do I get the value of a form control?

>In HTML documents, a form may be referred to as a property of the
>`document.forms` collection, either by its ordinal index or by name
>(if the `form` has a name).

There are at least two other ways if getting a reference to a form, not
counting perambulating the DOM structure from somewhere nearby.


> A `form`'s controls may be similarly referenced
>from its `elements` collection:
>
>var frm = document.forms[0];
>var control = frm.elements["elementname"];

var control = frm.elementname;

is simpler, where applicable (which is usually).



>First Exception: Where the control is a `SELECT` element, and
>support for older browsers, such as NN4, is required:

NN4 was superseded almost 10 years ago, according to
<http://en.wikipedia.org/wiki/Timeline_of_web_browsers>. Its usage
share must now be insignificant.

>var value = control.options[control.selectedIndex].value;
>
>Second Exception: Where several controls share the same name,
>such as radio buttons.

There, "such as" seems to call for mote than one example.


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