attribute name problem

Dennis

This doesn't work:
<head>

<script>
function display()
{
alert("hey");
}
</script>
</head>
<body>
<form >
<input type="button"
name="display" 
value="Display All"
onclick="display()" />
</form>
</body>

But with one character different, this does:


<form >
<input type="button"
name="displa" 
value="Display All"
onclick="display()" />
</form>
The difference is in the name attribute. I can name it "displa",
"displays", "displat", or "displa*" and it works. But when I call it
"display" it doesn't work.

Why?
Thanks.
Dennis

Jul 23 '05 #1

Subscribe Post Reply

1170

Lasse Reichstein Nielsen

ml***@yahoo.com (Dennis) writes:

function display() <input type="button"
name="display" 
The problem is that you are using IE, and IE has decided to make all
named elements available as properties of the global object (i.e., as
global variables).

That means that the global variable "display", which starts out
pointing to the function, is overwritten with a reference to the input
element.
onclick="display()" />
So this fails because "display" is not a function.
But when I call it "display" it doesn't work.

"doesn't work" is about as useless as an error report can be.
My *guess* is that you get an error message (or would get one if you
have error messages enabled, which you should) saying that "display"
is not a function.

/L
--
Lasse Reichstein Nielsen - lr*@hotpop.com
DHTML Death Colors: <URL:http://www.infimum.dk/HTML/rasterTriangleDOM.html>
'Faith without judgement merely degrades the spirit divine.'

Jul 23 '05 #2

Michael Winter

On 7 Aug 2004 11:08:58 -0700, Dennis <ml***@yahoo.com> wrote:

[snip]

The difference is in the name attribute. I can name it "displa",
"displays", "displat", or "displa*" and it works. But when I call it
"display" it doesn't work.

Why?

As I'm sure you're aware, most browsers accept the shortcut form/control
accessor that looks like:

document.formName.controlName

In order for this to work, every named form (formName, above) is made a
property of the document object. Likewise, every named form control is
made a property of its parent form.

When the intrinsic event for a form control is executed, the form object
itself is added, for reasons unknown to me, to the scope chain. This scope
chain is used to resolve identifiers. As I already mentioned, named form
controls are added to the form object as properties, so if you use a
control name as an identifier, it will be found in the form. This is why
renaming the form control (or the function) produces the more desired
results: the name you're looking for can't be found in the form object, so
the browser looks to the global object and finds it there[1].

It should be noted that this only occurs when the form control is
contained within a form. If it's by itself, only the control itself, and
the global object, are part of the scope chain[2].

Mike

[1] Apologies for any discrepancies in that description - my knowledge of
the scope chain is a little fuzzy, particularly as to why the form is
added.
[2] Well, that's what I've seen anyway.

--
Michael Winter
Replace ".invalid" with ".uk" to reply by e-mail

Jul 23 '05 #3

Michael Winter

On Sat, 07 Aug 2004 20:42:40 +0200, Lasse Reichstein Nielsen
<lr*@hotpop.com> wrote:

ml***@yahoo.com (Dennis) writes:
function display()

<input type="button"
name="display" 

The problem is that you are using IE, and IE has decided to make all
named elements available as properties of the global object (i.e., as
global variables).

I thought that at first, but Opera and Mozilla also display the same
behaviour. See my other post for my explanation. Am I correct?

[snip]

Mike

--
Michael Winter
Replace ".invalid" with ".uk" to reply by e-mail

Jul 23 '05 #4

Richard Cornford

Michael Winter wrote:
<snip>

It should be noted that this only occurs when the form
control is contained within a form. If it's by itself,
only the control itself, and the global object, are
part of the scope chain[2].

<snip>

The exact scope chain created by various browsers varies enormously
(including some that do not modify the normal JS scope chain with only
the global object on it), and can depend on the context in which the
element appears. Mozilla has a strong tendency to add all ancestors in
the DOM tree to the scope chin of elements outside of forms.

Google for an exchange between Dom Leonard and me with the subject
"Works in ie and opera not mozilla" for code to examine the scope chain
in various browsers.

Richard.

Jul 23 '05 #5

Lasse Reichstein Nielsen

"Michael Winter" <M.******@blueyonder.co.invalid> writes:

When the intrinsic event for a form control is executed, the form
object itself is added, for reasons unknown to me, to the scope
chain.
I believe this convenience feature was added in the early Netscape
versions.
It should be noted that this only occurs when the form control is
contained within a form. If it's by itself, only the control itself,
and the global object, are part of the scope chain[2].

And the document element. It's only the form element that is missing.

Which elements is added to the scope chain depends on the browser. At
least Opera 5+ and Netscape 2 omit the document element from the scope
chain. Opera 4 has no special scope chain at all, so only the global
object is visible. Other browsers (Netscape 3+, Mozilla FF, IE 4+)
has a scope chain consisting of the global object, document, the form
and the form control. For all but NS4, an input element outside a form
still has the document object and itself in the scope chain (NS4 can't
understand input elements outside of a form).

I haven't checked, e.g., Macintosh browers.
/L
--
Lasse Reichstein Nielsen - lr*@hotpop.com
DHTML Death Colors: <URL:http://www.infimum.dk/HTML/rasterTriangleDOM.html>
'Faith without judgement merely degrades the spirit divine.'

Jul 23 '05 #6

Dennis

>"doesn't work" is about as useless

as an error report can be.

Yes. It sure is. Please forgive my carelessness.

"doesn't work" means that the page loads just fine, but when I hit the
*display* button I get the message "Object doesn't support this
property or method," and the function is never called. The function,
defined elsewhere on the page, is supposed to display an array of
records the user has entered. According to the tutorial I'm using the
error message doesn't make sense (to me) because I'm using standard
properties.

Dennis

Jul 23 '05 #7

Dennis

>As I'm sure you're aware, . .

Actually, this is my first attempt with Javascript, and my second
attempt with html. I'm definitely a newbie.

Thanks for the explanation.

Dennis

Jul 23 '05 #8

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