Subj : E4X in Rhino expandos seem buggy
To   : netscape.public.mozilla.jseng
From : Mark Turansky
Date : Wed May 25 2005 10:16 am

I'm using Java 1.4.2 on W2K and Rhino 1.6.

First, the "e4x_examples.js" file runs perfectly well, which lead to my
discovering of buggy or at least inconsistent behavior when building XML
strings using expandos.

In the examples, a new "order" node is created with this statement:

order.item[0] = "";
order.item[0].description = "Small Rodents";

The most important thing to note here is the index [0], because in my script
below this will not work.

This fails with "Error in javascript: TypeError: undefined is not an xml
object. (C:\projects\jsx\root\testhtml.jss#8)".     Line 14 is

1   var html = <html/>;
2  html.head.title = "My Page Title";
3  html.body.@bgcolor = "#e4e4e4";
4  html.body.form.@name = "myform";
5  html.body.form.@action = "someurl.jss";
6  html.body.form.@method = "post";
7  html.body.form.@onclick = "return somejs()";
8  html.body.form.input[0].@name = "test";          // also fails if line 7
is:    html.body.form.input[0] = ""


But this works:

8   html.body.form.input.@name = "test";


If I want to add new "input" nodes (and what html form doesn't have many?),
this works:

9    html.body.form.input[1] = ""
10  html.body.form.input[1].@name = "testing";

but leaving line 9 out causes an 'undefined' error like above.

Why would it be undefined without line 9 when line 8 above doesn't require
initialization with an empty string?

Why does "input[0]" not work for me, but it works in the examples?


I'm glad I am able to figure out its behavior and make it work, but it feels
like a hack to add empty strings to elements with [1] but not to [0].   I
very much prefer lines like #3, where I just declare the attribute of the
node and the node itself is created.

On the bright side, using the now-known workarounds that I've discovered,
the above script produces perfect xhtml.

Mark

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