Title says it. If I use a for in loop on an HTML collection, I get
length twice.
<!DOCTYPE HTML>
<html lang="en">
<head>
<title>length twice</title>
</head>
<body>
<form action="javascr ipt:;" id="form1">
<input name="length" type="text"/>
</form>
<script type="text/javascript">
var f = document.forms[0].elements, a=[];
for(p in f) {
a.push('"'+p+'" : ' + f[p]);
}
document.write( "<xmp>"+a.join( ",\n")+"<"+ "/xmp>");
</script>
</body>
</html>
Opera:
"0" : [object HTMLInputElemen t],
"length" : [object HTMLInputElemen t],
"length" : [object HTMLInputElemen t],
"item" : function item() { [native code] },
"namedItem" : function namedItem() { [native code] },
"tags" : function tags() { [native code] }
However, length only appears twice way if the element named -length- is
present. Otherwise, the length property only appears once, and has the
"normal" value of the number of form controls.
What could be happening here? I suspect that there may be an object in
the prototype with a - length - property, but can't verify this.
hasOwnProperty always returns false.
Garrett
15  2006 
dhtml wrote:
Title says it. If I use a for in loop on an HTML collection, I get
length twice.
(in Opera)
>
Garrett
dhtml wrote:
<!DOCTYPE HTML>
<html lang="en">
<head>
* *<title>length twice</title>
</head>
<body>
<form action="javascr ipt:;" id="form1">
* * * * <input name="length" type="text"/>
</form>
<script type="text/javascript">
var f = document.forms[0].elements, a=[];
for(p in f) {
* *a.push('"'+p+' " : ' + f[p]);}
document.write( "<xmp>"+a.join( ",\n")+"<"+ "/xmp>");
</script>
</body>
</html>
Opera:
"0" : [object HTMLInputElemen t],
"length" : [object HTMLInputElemen t],
"length" : [object HTMLInputElemen t],
"item" : function item() { [native code] },
"namedItem" : function namedItem() { [native code] },
"tags" : function tags() { [native code] }
However, length only appears twice way if the element named -length- is
present. Otherwise, the length property only appears once, and has the
"normal" value of the number of form controls.
What could be happening here? I suspect that there may be an object in
the prototype with a - length - property, but can't verify this.
hasOwnProperty always returns false.
The one refers to your user-defined object
document.forms[0].elements['length'] (multi-dimensional, accessible by
its properties/methods) and the other to the syntactically identical
host object (but as a one-dimensional immatricial variable).
Your test does not show the same result in my Opera 9.22.8801; there
the user-defined object appears to overwrite the host object.
It is never good to give names like "length" to user-defined objects.
--
Bart
On Sep 2, 5:50*am, dhtml <dhtmlkitc...@g mail.comwrote:
dhtml wrote:
Title says it. If I use a for in loop on an HTML collection, I get
length twice.
(in Opera)
Garrett
AVOID using predefined [reserved] var names for your own vars/fields...
GArlington wrote:
On Sep 2, 5:50 am, dhtml <dhtmlkitc...@g mail.comwrote:
>dhtml wrote:
>>Title says it. If I use a for in loop on an HTML collection, I get
length twice.
(in Opera)
>>Garrett
AVOID using predefined [reserved] var names for your own vars/fields...
Yes, of course.
I used an element named "length" on purpose. The goal is to learn about
the browser.
The for in loop should not expose the same key twice. I wonder what
Opera is doing.
Garrett
On Sep 2, 5:44*pm, dhtml <dhtmlkitc...@g mail.comwrote:
GArlington wrote:
On Sep 2, 5:50 am, dhtml <dhtmlkitc...@g mail.comwrote:
dhtml wrote:
Title says it. If I use a for in loop on an HTML collection, I get
length twice.
(in Opera)
>Garrett
AVOID using predefined [reserved] var names for your own vars/fields...
Yes, of course.
I used an element named "length" on purpose. The goal is to learn about
the browser.
The for in loop should not expose the same key twice. I wonder what
Opera is doing.
Garrett
I can reproduce this in ver. 9.51 (build 4886) on Mac OS X (10.5.4)
Moreover, when element with name="toString" is present, any attempt to
obtain a reference to a form element (containing that element)
produces an error:
"The Object does not implement [[Call]]"
--
kangax
On Sep 3, 7:44*am, dhtml <dhtmlkitc...@g mail.comwrote:
GArlington wrote:
On Sep 2, 5:50 am, dhtml <dhtmlkitc...@g mail.comwrote:
dhtml wrote:
Title says it. If I use a for in loop on an HTML collection, I get
length twice.
(in Opera)
>Garrett
AVOID using predefined [reserved] var names for your own vars/fields...
Yes, of course.
I used an element named "length" on purpose. The goal is to learn about
the browser.
The for in loop should not expose the same key twice.
As far as I can determine, ECMA-262 doesn't specify that property
names must be unique, though clearly there are issues if they aren't.
It also lets host objects do pretty much as they please.
I wonder what Opera is doing.
It can do what it likes as long as it conforms to to ECMA-262. How it
chooses to reference properties internally for [[Get]] and [[Put]] is
up to Opera, the spec says in regard to internal methods (bottom of
Section 8.6.2):
"Host objects may implement these methods in any manner unless
specified otherwise; for example, one possibility is that
[[Get]] and [[Put]] for a particular host object indeed fetch
and store property values but [[HasProperty]] always generates
false"
--
Rob
RobG wrote:
On Sep 3, 7:44 am, dhtml <dhtmlkitc...@g mail.comwrote:
>GArlington wrote:
>>On Sep 2, 5:50 am, dhtml <dhtmlkitc...@g mail.comwrote:
dhtml wrote:
Title says it. If I use a for in loop on an HTML collection, I get
length twice.
(in Opera)
Garrett
AVOID using predefined [reserved] var names for your own vars/fields...
Yes, of course.
I used an element named "length" on purpose. The goal is to learn about
the browser.
The for in loop should not expose the same key twice.
As far as I can determine, ECMA-262 doesn't specify that property
names must be unique, though clearly there are issues if they aren't.
It also lets host objects do pretty much as they please.
Here's my guess on Opera's behavior:
Opera is Enumerating over the object and the interface for
HTMLCollection to get enumerable keys.
But that's just my guess.
Garrett
--
Rob
kangax wrote:
On Sep 2, 5:44 pm, dhtml <dhtmlkitc...@g mail.comwrote:
>GArlington wrote:
>>On Sep 2, 5:50 am, dhtml <dhtmlkitc...@g mail.comwrote:
dhtml wrote:
Title says it. If I use a for in loop on an HTML collection, I get
length twice.
(in Opera)
Garrett
AVOID using predefined [reserved] var names for your own vars/fields...
Yes, of course.
I used an element named "length" on purpose. The goal is to learn about
the browser.
The for in loop should not expose the same key twice. I wonder what
Opera is doing.
Garrett
I can reproduce this in ver. 9.51 (build 4886) on Mac OS X (10.5.4)
I'm still on 10.4. No iphone emulator.
Moreover, when element with name="toString" is present, any attempt to
obtain a reference to a form element (containing that element)
produces an error:
javascript :aler t(document.form s[0].elements.toStr ing);
javascript :aler t(document.form s[0].toString);
I don't get the error.
Only with:
javascript :aler t(document.form s[0]);
Because the alert method is probably trying to get the DefaultValue and
ends up calling document.forms[0].toString, but
document.forms[0].toString is an element.
Garrett
"The Object does not implement [[Call]]"
--
kangax
In comp.lang.javas cript message <g9**********@r egistered.motza rella.org>
, Mon, 1 Sep 2008 21:41:41, dhtml <dh**********@g mail.composted:
>Title says it.
Body of an article should stand alone, without reference to Subject -
S(N)OP. Bug reports should include browser version.
If I use a for in loop on an HTML collection, I get length twice.
MS IE 7.0.5730.13 - long list, length twice
Safari 3.1.2 - short list, length once
Firefox 2.0.0.16 - short list, length once
Opera 9.27 - short list, length once
It's a good idea to read the newsgroup c.l.j and its FAQ. See below.
--
(c) John Stockton, nr London UK. ?@merlyn.demon. co.uk IE7 FF2 Op9 Sf3
news:comp.lang. javascript FAQ <URL:http://www.jibbering.c om/faq/index.html>.
<URL:http://www.merlyn.demo n.co.uk/js-index.htmjscr maths, dates, sources.
<URL:http://www.merlyn.demo n.co.uk/TP/BP/Delphi/jscr/&c, FAQ items, links. This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics | |
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