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Array function SPLICE doesn't work with Select->OPTIONS array. JavaScript

P: n/a
Hi,
I have had to invent a work-around to get past what looks like a
JavaScript bug, the malfunctioning Perl-like JavaScript array functions
including SPLICE() and UNSHIFT().

I have boiled it down to a very simple test case which can be
cut-n-pasted into a .html file and viewed in a browser:

================================================== ==========================

<META HTTP-EQUIV="expires" VALUE="Tue, 23 Jun 1998 01:46:05
GMT"><!DOCTYPE html
PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" lang="en-US"
xml:lang="en-US">
<head>
<title>Weird JavaScript Array Function Malfunction!</title>
<meta name="expires" content="Tue, 23 Jun 1998 01:46:05 GMT" />
<script type="text/javascript">//<![CDATA[

function resort() {
var sortara = new Array;
sortara = document.aceform.sort.options;
var length = sortara.length;
alert("SortAra length = " + sortara.length)
var selidx = document.aceform.sort.selectedIndex;
alert("Selected Index = " + selidx);
var selected = sortara[selidx];
alert("Selected item = " + selected.text);
selected = sortara.splice(selidx, 1); // Remove selected array item.
alert("Selected item = " + selected.text); // Never gets here.
Error.
sortara.unshift(selected); // Insert item at top of array.

}

//]]></script>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"
/>
</head>
<body bgcolor="#B0CEBE">
<form method="post" action="" enctype="multipart/form-data"
name="aceform">
<center>

<table border="2" cellspacing="2" cellpadding="2">
<tr><td><center>Sort</td></tr>
<tr><td align="center">
<select name="sort" size="4" onchange="resort(this)">
<option value="Item1">Item1</option>
<option value="Item2">Item2</option>
<option value="Item3">Item3</option>
<option value="Item4">Item4</option>
</select></td>
</tr>
</table>
</center><div></div></form>
</body>
</html>
================================================== =======================

The intent of this script is to move the selected item to the to of the
menu. What could be simpler? Something similar to the Perl one-liner:
unshift(@array, splice(@array, $selectIndex, 1)); # Move SelIdx item
to top.

In a JavaScript console in Firefox 1.0.6 as well as in Opera and
evilnet explorer, I get the error message, "Error: sortara.splice is
not a function". Sortara is valued with
"document.aceform.sort.options", and options is an array.

The first 3 alerts show exactly what they should. The array length
comes out to 4, the selected item shows 3 if I click on the last item,
and the item description matches my selection, "Item3" if I choose the
last one. The final alert is never reached, but instead the JavaScript
terminates and a new error message (above) is written to the JS
console.

The 'Reilly Rhino book, "JavaScript, The Definitive Guide" documents
the select object's OPTIONS property as, "An ARRAY of option objects
...."

I can only find 3 hits on this in Google. Is this a real JavaScript bug
or am I loosing it?

THX,

BrianP

Sep 17 '05 #1
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2 Replies


P: n/a


BrianP wrote:

var sortara = new Array;
sortara = document.aceform.sort.options;
var length = sortara.length;
alert("SortAra length = " + sortara.length)
var selidx = document.aceform.sort.selectedIndex;
alert("Selected Index = " + selidx);
var selected = sortara[selidx];
alert("Selected item = " + selected.text);
selected = sortara.splice(selidx, 1); // Remove selected array item. In a JavaScript console in Firefox 1.0.6 as well as in Opera and
evilnet explorer, I get the error message, "Error: sortara.splice is
not a function". Sortara is valued with
"document.aceform.sort.options", and options is an array.


You may think that options is an array but DOM collections are usually
not implemented as JavaScript arrays in current browsers. The options
property of a select gives you a DOM collection and while that has a
length property and some properties you can access with a number index
that does not mean the object is an Array object instance implementing
all methods that native Array object instances have.
So the error message tells you that the DOM object you are trying to
call a 'splice' method on does not have that method.

The W3C DOM specification lists
<http://www.w3.org/TR/DOM-Level-2-HTML/html.html#ID-30606413>
so in a browser following that specification options implements the
HTMLOptionsCollection interface
<http://www.w3.org/TR/DOM-Level-2-HTML/html.html#HTMLOptionsCollection>
where you have a length property and two methods item and namedItem.
Within ECMAScript implementations of the DOM
<http://www.w3.org/TR/DOM-Level-2-HTML/ecma-script-binding.html> you can
then use
options[index]
instead of
options.item(index)
and
options[name]
instead of
options.namedItem(name)

But that is all the DOM suggests, nothing requiring or suggesting that
there are any methods native JavaScript arrays implement.
--

Martin Honnen
http://JavaScript.FAQTs.com/
Sep 17 '05 #2

P: n/a
BrianP wrote:
Hi,
I have had to invent a work-around to get past what looks like a
JavaScript bug, the malfunctioning Perl-like JavaScript array functions
including SPLICE() and UNSHIFT().

I have boiled it down to a very simple test case which can be
cut-n-pasted into a .html file and viewed in a browser:

================================================== ==========================

<META HTTP-EQUIV="expires" VALUE="Tue, 23 Jun 1998 01:46:05
GMT"><!DOCTYPE html
PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" lang="en-US"
xml:lang="en-US">
<head>
<title>Weird JavaScript Array Function Malfunction!</title>
<meta name="expires" content="Tue, 23 Jun 1998 01:46:05 GMT" />
<script type="text/javascript">//<![CDATA[

function resort() {
var sortara = new Array;
sortara = document.aceform.sort.options;
var length = sortara.length;
alert("SortAra length = " + sortara.length)
var selidx = document.aceform.sort.selectedIndex;
alert("Selected Index = " + selidx);
var selected = sortara[selidx];
alert("Selected item = " + selected.text);
selected = sortara.splice(selidx, 1); // Remove selected array item.
alert("Selected item = " + selected.text); // Never gets here.
Error.
sortara.unshift(selected); // Insert item at top of array.

}

//]]></script>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"
/>
</head>
<body bgcolor="#B0CEBE">
<form method="post" action="" enctype="multipart/form-data"
name="aceform">
<center>

<table border="2" cellspacing="2" cellpadding="2">
<tr><td><center>Sort</td></tr>
<tr><td align="center">
<select name="sort" size="4" onchange="resort(this)">
<option value="Item1">Item1</option>
<option value="Item2">Item2</option>
<option value="Item3">Item3</option>
<option value="Item4">Item4</option>
</select></td>
</tr>
</table>
</center><div></div></form>
</body>
</html>
================================================== =======================

The intent of this script is to move the selected item to the to of the
menu. What could be simpler? Something similar to the Perl one-liner:
unshift(@array, splice(@array, $selectIndex, 1)); # Move SelIdx item
to top.

In a JavaScript console in Firefox 1.0.6 as well as in Opera and
evilnet explorer, I get the error message, "Error: sortara.splice is
not a function". Sortara is valued with
"document.aceform.sort.options", and options is an array.

The first 3 alerts show exactly what they should. The array length
comes out to 4, the selected item shows 3 if I click on the last item,
and the item description matches my selection, "Item3" if I choose the
last one. The final alert is never reached, but instead the JavaScript
terminates and a new error message (above) is written to the JS
console.

The 'Reilly Rhino book, "JavaScript, The Definitive Guide" documents
the select object's OPTIONS property as, "An ARRAY of option objects
..."


As Martin said, element collections are not arrays.

If it helps, here's a thread here that shows how to put references to
the options into an array. Once you've done that you can use the array
methods on the array of references then re-build the select using just
the options that are left (or have been added maybe).

<URL:http://groups.google.com/group/comp.lang.javascript/browse_frm/thread/7074abbe73943dcb/2d46c041ee36bc60?q=Combining+object+arrays&rnum=1& hl=en#2d46c041ee36bc60>

Just remember that your array will be references to the options, not the
actual options. If you show what you are trying to do with the options,
then maybe more help can be provided.

--
Rob
Sep 18 '05 #3

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