Add-ons using the techniques described in this document are considered a legacy technology in Firefox. Don't use these techniques to develop new add-ons. Use WebExtensions instead. If you maintain an add-on which uses the techniques described here, consider migrating it to use WebExtensions.
From Firefox 53 onwards, no new legacy add-ons will be accepted on addons.mozilla.org (AMO).
From Firefox 57 onwards, WebExtensions will be the only supported extension type, and Firefox will not load other types.
Even before Firefox 57, changes coming up in the Firefox platform will break many legacy extensions. These changes include multiprocess Firefox (e10s), sandboxing, and multiple content processes. Legacy extensions that are affected by these changes should migrate to WebExtensions if they can. See the "Compatibility Milestones" document for more.
A wiki page containing resources, migration paths, office hours, and more, is available to help developers transition to the new technologies.
Here is an implementation of Node.lookupNamespaceURI which should work cross-browser.
/*globals Document, HTMLDocument */
(function () {
'use strict';
var Doc = typeof Document !== 'undefined' ? Document : HTMLDocument; // Support HTMLDocument if Document not present // If Document is present, is this method also present?
addLookupNamespaceURI(Doc);
addLookupNamespaceURI(Element);
function addLookupNamespaceURI (type) {
if (!type.prototype.lookupNamespaceURI) {
type.prototype.lookupNamespaceURI = lookupNamespaceURI;
}
function lookupNamespaceURI (prefix) {
return lookupNamespaceURIHelper(this, prefix);
}
function lookupNamespaceURIHelper (node, prefix) { // adapted directly from http://www.w3.org/TR/DOM-Level-3-Core/namespaces-algorithms.html#lookupNamespaceURIAlgo
var i, att,
htmlMode = document.contentType, // Mozilla only
xmlnsPattern = /^xmlns:(.*)$/;
switch (node.nodeType) {
case 1: // ELEMENT_NODE (could also just test for Node.ELEMENT_NODE, etc., if supported in all browsers)
if (node.namespaceURI != null && node.prefix === prefix) {
// Note: prefix could be "null" in the case we are looking for default namespace
return node.namespaceURI;
}
if (node.attributes.length) {
for (i = 0; i < node.attributes.length; i++) {
att = node.attributes[i];
if (xmlnsPattern.test(att.name) && xmlnsPattern.exec(att.name)[1] === prefix) {
if (att.value) {
return att.value;
}
return null; // unknown
}
if (att.name === 'xmlns' && prefix == null) {
// default namespace
if (att.value) {
return att.value;
}
return null; // unknown
}
}
}
if (node.parentNode && node.parentNode.nodeType !== 9) {
// EntityReferences may have to be skipped to get to it
return lookupNamespaceURIHelper(node.parentNode, prefix);
}
return null;
case 9: // DOCUMENT_NODE
return lookupNamespaceURIHelper(node.documentElement, prefix);
case 6: // ENTITY_NODE
case 12: // NOTATION_NODE
case 10: // DOCUMENT_TYPE_NODE
case 11: // DOCUMENT_FRAGMENT_NODE
return null; // unknown
case 2: // ATTRIBUTE_NODE
if (node.ownerElement) {
return lookupNamespaceURIHelper(node.ownerElement, prefix);
}
return null; // unknown
default:
// TEXT_NODE (3), CDATA_SECTION_NODE (4), ENTITY_REFERENCE_NODE (5),
// PROCESSING_INSTRUCTION_NODE (7), COMMENT_NODE (8)
if (node.parentNode) {
// EntityReferences may have to be skipped to get to it
return lookupNamespaceURIHelper(node.parentNode, prefix);
}
return null; // unknown
}
};
}
}());