Attr: namespaceURI property
The read-only namespaceURI
property of the Attr
interface returns the namespace URI of the attribute,
or null
if the element is not in a namespace.
The namespace URI is set at the Attr
creation and cannot be changed.
An attribute with a namespace can be created using Element.setAttributeNS()
.
Note: 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 browser does not handle or enforce namespace validation per se. It is up to the JavaScript application to do any necessary validation. Note, too, that the namespace prefix, once it is associated with a particular attribute node, cannot be changed.
Value
A string containing the URI of the namespace, or null
if the attribute is not in a namespace.
Example
The following example shows the results for a prefixed attribute in a case of an HTML element, and of a SVG element.
As HTML doesn't handle namespaces, it will always return null
in that case.
In the case of the SVG element, it will return the URI of the XML namespace, http://www.w3.org/XML/1998/namespace
.
HTML
<svg xml:lang="en-US" class="struct" height="1" width="1">Click me</svg>
<label xml:lang="en-US" class="struct"></label>
<p>
<button>Show value for <svg></button>
<button>Show value for <label></button>
</p>
<p>
Namespace URI of the attribute <code>xml:lang</code>:
<output id="result">None.</output>
</p>
JavaScript
const elements = document.querySelectorAll(".struct");
const buttons = document.querySelectorAll("button");
const outputEl = document.querySelector("#result");
let i = 0;
for (const button of buttons) {
const element = elements[i];
button.addEventListener("click", () => {
const attribute = element.attributes[0];
outputEl.value = attribute.namespaceURI;
});
i++;
}
Specifications
Specification |
---|
DOM Standard # dom-attr-namespaceuri |
Browser compatibility
BCD tables only load in the browser
See also
- The properties
Attr.name
, returning the qualified name of the attribute,Attr.localName
, the local part of the name, andAttr.prefix
, the namespace prefix. - The
Element.namespaceURI
property, equivalent to this one but for anElement
. - The
Element.setAttributeNS()
method, creating an attribute with a given namespace.