Get default namespace from XMLDocument in JS

Question

I loaded XMLDocument with XMLHttpRequest.

<root xmlns="http://somesite.org/ns">
</root>

http://somesite.org/ns is the default namespace. I can use function Node.isDefaultNamespace for check if some namespace is default (true/false) and it's work well.

But how can I get default namespace from XMLDocument?

Is there somethink like DOMString Node.getDefaultNamespace()?

Martin Honnen · Accepted Answer · 2016-09-04 17:35:07Z

1

Use lookupNamespaceURI(null):

var parser = new DOMParser();
[
  '<root xmlns="http://example.com/ns1"/>',
  '<root/>',
  '<ns:root xmlns:ns="example.com/ns2"/>'
].forEach(function(item) {
  var doc = parser.parseFromString(item, "application/xml");
  console.log('result of doc.lookupNamespaceURI(null): |' + doc.lookupNamespaceURI(null) + '|');
});

According to https://www.w3.org/TR/dom/#dom-node-lookupnamespaceuri, it should also work to use lookupNamespaceURI(''):

var parser = new DOMParser();
['<root xmlns="http://example.com/ns1"/>',
 '<root/>',
 '<ns:root xmlns:ns="example.com/ns2"/>'].forEach(function(item) {
  var doc = parser.parseFromString(item, "application/xml");
  console.log('result of doc.lookupNamespaceURI(\'\'): |' + doc.lookupNamespaceURI('') + '|');
});

Keep in mind that XML allows you to override the default namespace on any element so the result of doc.lookupNamespaceURI('') checks the documentElement and there can be children or descendants using a different or no default namespace.

edited Sep 4, 2016 at 17:35

answered Sep 4, 2016 at 12:05

Martin Honnen

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9 Comments

Iaroslav Baranov Over a year ago

It doesn't work. >myXML #document <root xmlns="http://www.w3.org/TR/html77/"></root> >myXML.lookupNamespaceURI('') null

Martin Honnen Over a year ago

My answer contains an executable code snippet which works fine for me in current versions of Edge, Chrome, Firefox and IE on Windows 10. So in which environment have you run your code which does return null?

nwellnhof Over a year ago

On Chrome/OS X, only doc.lookupNamespaceURI(null) works which is also what MDN says.

Martin Honnen Over a year ago

w3.org/TR/dom/#dom-node-lookupnamespaceuri specifies "If prefix is the empty string, set it to null. " in the algorithm for that method. But it looks as you are right on Chrome, somehow in my previous test I overlooked that the snippet shows null. I will edit the answer.

nwellnhof Over a year ago

Seems to be a new feature in DOM4. This sentence is missing from the DOM Level 3 spec.

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