MDN’s new design is in Beta! A sneak peek:



Node.namespaceURI 是一个只读属性,返回节点的命名空间URI(namespace URI),如果节点不在一个命名空间中,则返回 null。当节点是文档节点时,返回当前文档的 XML 命名空间(namespace)。


namespace = node.namespaceURI


In this snippet, a node is being examined for its localName and its namespaceURI. If the namespaceURI returns the XUL namespace and the localName returns "browser", then the node is understood to be a XUL <browser/>.

if (node.localName == "browser" && 
    node.namespaceURI == "") {
  // this is a XUL browser 


This is not a computed value that is the result of a namespace lookup based on an examination of the namespace declarations in scope. The namespace URI of a node is frozen at the node creation time.

In Firefox 3.5 and earlier, the namespace URI for HTML elements in HTML documents is null. In later versions, in compliance with HTML5, it is as in XHTML.

For nodes of any nodeType other than ELEMENT_NODE and ATTRIBUTE_NODE the value of namespaceURI is always null.

You can create an element with the specified namespaceURI using the DOM Level 2 method document.createElementNS.

Per the Namespaces in XML specification, an attribute does not inherit its namespace from the element it is attached to. If an attribute is not explicitly given a namespace, it has no namespace.

The DOM does not handle or enforce namespace validation per se. It is up to the DOM application to do any validation necessary. Note too that the namespace prefix, once it is associated with a particular node, cannot be changed.



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