mozilla and XPath Expressions

Neil Zanella · Dec 9, 2003

Hello,

I would like to know whether the mozilla web browser has built in support
for searching XML documents via XPath expressions as with IE's xmlobject's
and xmlDoc's function selectNodes() or similar.

Thanks!

Neil

Martin Honnen · Dec 9, 2003

Neil said:
I would like to know whether the mozilla web browser has built in support
for searching XML documents via XPath expressions as with IE's xmlobject's
and xmlDoc's function selectNodes() or similar.

Mozilla has XPath support but not the restricted MSXML selectNodes but
rather a more complete approach that is being under development, Mozilla
attempts to implement the W3C DOM Level 3 XPath module:
http://www.w3.org/TR/2003/CR-DOM-Level-3-XPath-20030331/

At the heart of that is method
document.evaluate(
string xpathexpression,
node contextNode,
XPathNSResolver namespaceresolver,
number desiredResultType,
object resultObject
)

Some examples on how to use it, lets create a short example document first:

var xmlSource = '';
xmlSource += '<gods>';
xmlSource += '<god name="Kibo" />';
xmlSource += '<god name="Xibo" />';
xmlSource += '<\/gods>';
var xmlDocument = new DOMParser().parseFromString(xmlSource, 'text/xml');

var xmlSerializer = new XMLSerializer();

Selecting a single node:

var xpathResult = xmlDocument.evaluate(
'//god',
xmlDocument,
null,
9,
null
);

if (xpathResult.singleNodeValue) {
alert(xmlSerializer.serializeToString(xpathResult.singleNodeValue));
}

Selecting an ordered node list:

var xpathResult = xmlDocument.evaluate(
'//god',
xmlDocument,
null,
5,
null
);

var resultNode;

while ((resultNode = xpathResult.iterateNext())) {
alert(xmlSerializer.serializeToString(resultNode));
}

Evaluating an expression that returns a number:

var xpathResult = xmlDocument.evaluate(
'count(//*/@*)',
xmlDocument,
null,
0,
null
);

if (xpathResult.resultType == 1) {
alert('Counted ' + xpathResult.numberValue + ' nodes.');
}

That should help you to get started if you then have a look at the
specification.
Or ask here if you have further questions.
There is even some attempt to extend XPath to HTML documents:

<html>
<head>
<title>"XPath" on HTML in Mozilla</title>
<script type="text/javascript">
function countCenteredParagraphs () {
if (typeof document.evaluate != 'undefined') {
var xpathResult =
document.evaluate(
'count(//p[@align = "center"])',
document,
null,
1,
null
);
alert('Found ' + xpathResult.numberValue + ' centered paragraphs.');
}
}
window.onload = countCenteredParagraphs;
</script>
</head>
<body>
<p align="center">
A paragraph with centered text.
</p>
<p align="center">
A second paragraph with centered text.
</p>
</body>
</html>

Neil Zanella · Dec 14, 2003

Martin Honnen said:
Mozilla has XPath support but not the restricted MSXML selectNodes but
rather a more complete approach that is being under development, Mozilla
attempts to implement the W3C DOM Level 3 XPath module:
http://www.w3.org/TR/2003/CR-DOM-Level-3-XPath-20030331/

Thank you for your reply. I recently upgraded to mozilla 1.4.1 and I can see
that it has a "DOM Inspector" feature accessible from the menu bar under
Tools -> Web Development. I guess this is what you must be referring to.
So how do I run the code snippets that you posted?

At the heart of that is method
document.evaluate(
string xpathexpression,
node contextNode,
XPathNSResolver namespaceresolver,
number desiredResultType,
object resultObject
)

Some examples on how to use it, lets create a short example document first:

var xmlSource = '';
xmlSource += '<gods>';
xmlSource += '<god name="Kibo" />';
xmlSource += '<god name="Xibo" />';
xmlSource += '<\/gods>';
var xmlDocument = new DOMParser().parseFromString(xmlSource, 'text/xml');

That should help you to get started if you then have a look at the
specification. Or ask here if you have further questions.
There is even some attempt to extend XPath to HTML documents:

Well, I thought that at least this should already be possible as far
as XHTML is concerned since XHTML is a reformulation of HTML as an XML
application, right?

Thanks!

Neil

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mozilla and XPath Expressions

Neil Zanella

Martin Honnen

Neil Zanella

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