DOM XPath query doesn't work when a xmlns is given

Question

In Firefox JavaScript console:

parser = new DOMParser();

foo = parser.parseFromString(\'\', \"text/xml\");
res = foo.evaluate(\"/foo\         


        

Answer 1

You have to do two things when dealing with namespaces.

1. Use the namespace in your XPath expression. As there is no prefix in your document, I just chose ns -- better go with something more descriptive in real world code.
2. Add a namespace resolver, which actually is a function that gets passed as third parameter to evaluate(...).

Putting everything together, your code would look like this:

parser = new DOMParser();
foo = parser.parseFromString('', "text/xml");
res = foo.evaluate("/ns:foo", foo, function(prefix) {
    if (prefix === 'ns') {
        return 'http://foo.bar.baz/quux';
    } else {
        return null
    }
}, 0, null);
res.iterateNext();

Which returns as expected:

---

Your third query has results because you're using the wildcard matcher * which ignores namespaces. An alternative XPath expression without registering a namespace, but using the wildcard matcher would be

//*[local-name() = 'foo']