Accessing elements of a form...

[Pawe³]

We can access the Nth element in the first form by

document.forms[0].elements[N]

imagine that theres function like
<INPUT TYPE=TEXT" onclick="somefunction(this)">
and...
we have

function somefunction(obj) {
how can we obtain the N from within the function???

[Michael Winter]

On Sat, 6 Mar 2004 12:41:31 +0100, Paweł <pm**@op.pl> wrote:

We can access the Nth element in the first form by

document.forms[0].elements[N]

imagine that theres function like
<INPUT TYPE=TEXT" onclick="somefunction(this)">
I assume that's a typo, and you meant: ... type="text" ... Note the
difference in quotes.
and...
we have

function somefunction(obj) {

how can we obtain the N from within the function???

obj
contains a reference to that INPUT element.
obj.form
will produce a reference to the INPUT element's containing form.
obj.form.elements[ N ]
will produce a reference to the Nth element of the INPUT element's
containing form.

Hope that helps,
Mike

--
Michael Winter
M.******@blueyonder.co.invalid (replace ".invalid" with ".uk" to reply)

[Pawe³]

On Sat, 06 Mar 2004 12:37:29 GMT, in comp.lang.javascript you wrote:

On Sat, 6 Mar 2004 12:41:31 +0100, Paweł <pm**@op.pl> wrote:

We can access the Nth element in the first form by

document.forms[0].elements[N]

imagine that theres function like
<INPUT TYPE=TEXT" onclick="somefunction(this)">

I assume that's a typo, and you meant: ... type="text" ... Note the
difference in quotes.

and...
we have

function somefunction(obj) {

how can we obtain the N from within the function???

obj
contains a reference to that INPUT element.
obj.form
will produce a reference to the INPUT element's containing form.
obj.form.elements[ N ]
will produce a reference to the Nth element of the INPUT element's
containing form.

Hope that helps,

Well it doesn't ...
What I ask about is how do we know that Nth element is Nth??
Let's say we have a row in the table, abd for each row we have rowIndex...
I would like to have similiar property for Input element...
Any ideas?

[Michael Winter]

On Sat, 6 Mar 2004 20:16:18 +0100, Paweł <pm**@op.pl> wrote:

[snip]

What I ask about is how do we know that Nth element is Nth??
Let's say we have a row in the table, abd for each row we have
rowIndex...
I would like to have similiar property for Input element...

You mean you want to know the index of a particular form control when you
have a reference (and only a reference) to that control?

There's no direct method. You'll have to loop through all controls in the
form and check if the "mystery" reference matches a reference in the
elements collection:

function getIndex( obj ) {
var e = obj.form.elements, n = e.length;

for( var i = 0; i < n; ++i )
if( obj == e[ i ]) return i;
return null;
}
...
<form ...>
<input type="button" onclick="alert(getIndex(this))">
<input type="button" onclick="alert(getIndex(this))">
</form>

Clicking on the first button will display 0. Clicking the second will
display 1.

Is that better?

Mike

--
Michael Winter
M.******@blueyonder.co.invalid (replace ".invalid" with ".uk" to reply)

[Pawe³]

function getIndex( obj ) {
var e = obj.form.elements, n = e.length;

for( var i = 0; i < n; ++i )
if( obj == e[ i ]) return i;
return null;
}
Is that better?

Yeah, that's obviously better. Thank you, currently I'm working on a script
to validate a form, and I would like my script to focus back on input field
in case user enters an incorrect value. So now, I can just call the focus
method on (N-1)th element and that should be fine I hope ;)