Questo articolo richiede una revisione tecnica. Scopri come puoi essere d’aiuto.
I volontari di MDN non hanno ancora tradotto questo articolo in Italiano. Registrati per tradurlo tu.
getAttributeNS returns the string value of the attribute with the specified namespace and name. If the named attribute does not exist, the value returned will either be null or "" (the empty string); see Notes for details.
Syntax
attrVal = element.getAttributeNS(namespace, name)
Parameters
namespace- The namespace in which to look for the specified attribute.
name- The name of the attribute to look for.
Return value
The string value of the specified attribute. If the attribute doesn't exist, the result is null.
Examples
The following SVG document reads the value of the foo attribute in a custom namespace.
<svg xmlns="https://www.w3.org/2000/svg"
xmlns:test="https://www.example.com/2014/test" width="40" height="40">
<circle id="target" cx="12" cy="12" r="10" stroke="#444"
stroke-width="2" fill="none" test:foo="Hello namespaced attribute!"/>
<script type="text/javascript">
var ns = 'https://www.example.com/2014/test';
var circle = document.getElementById( 'target' );
console.log( 'attribute test:foo: "' + circle.getAttributeNS( ns, 'foo' ) + '"' );
</script>
</svg>
In an HTML5 document the attribute has to be accessed with test:foo since namespaces are not supported.
<!DOCTYPE html>
<html>
<body>
<svg xmlns="https://www.w3.org/2000/svg"
xmlns:test="https://www.example.com/2014/test" width="40" height="40">
<circle id="target" cx="12" cy="12" r="10" stroke="#444" stroke-width="2"
fill="none" test:foo="Foo value"/>
</svg>
<script type="text/javascript">
var ns = 'https://www.example.com/2014/test';
var circle = document.getElementById( 'target' );
console.log('Attribute value: ' + circle.getAttribute('test:foo'));
</script>
</body>
</html>
Notes
Namespaces are only supported in XML documents. HTML5 documents have to use getAttribute() instead.
getAttributeNS() differs from getAttribute() in that it allows you to further specify the requested attribute as being part of a particular namespace, as in the example above, where the attribute is part of the fictional "specialspace" namespace on Mozilla.
Prior to the DOM4 specification, this method was specified to return an empty string rather than null for non-existent attributes. However, most browsers instead returned null. Starting with DOM4, the specification now says to return null. However, some older browsers return an empty string. For that reason, you should use hasAttributeNS() to check for an attribute's existence prior to calling getAttributeNS() if it is possible that the requested attribute does not exist on the specified element.
DOM methods dealing with element's attributes:
| Not namespace-aware, most commonly used methods | Namespace-aware variants (DOM Level 2) | DOM Level 1 methods for dealing with Attr nodes directly (seldom used) |
DOM Level 2 namespace-aware methods for dealing with Attr nodes directly (seldom used) |
|---|---|---|---|
setAttribute (DOM 1) |
setAttributeNS |
setAttributeNode |
setAttributeNodeNS |
getAttribute (DOM 1) |
getAttributeNS |
getAttributeNode |
getAttributeNodeNS |
hasAttribute (DOM 2) |
hasAttributeNS |
- | - |
removeAttribute (DOM 1) |
removeAttributeNS |
removeAttributeNode |
- |
Specifications
| Specification | Status | Comment |
|---|---|---|
| DOM The definition of 'Element.getAttributeNS()' in that specification. |
Living Standard | |
| Document Object Model (DOM) Level 3 Core Specification The definition of 'Element.getAttributeNS()' in that specification. |
Recommendation | Specifies that a NOT_SUPPORTED_ERR exception is thrown if the UA does not support the "XML" feature. Also specifies that null must be passed to have no namespace. |
| Document Object Model (DOM) Level 2 Core Specification The definition of 'Element.getAttributeNS()' in that specification. |
Recommendation | Initial definition |
Browser compatibility
| Feature | Chrome | Firefox (Gecko) | Internet Explorer | Opera | Safari |
|---|---|---|---|---|---|
| Basic support | (Yes) | (Yes)[1] | (Yes) | (Yes) | (Yes) |
| Feature | Android | Chrome for Android | Firefox Mobile (Gecko) | IE Mobile | Opera Mobile | Safari Mobile |
|---|---|---|---|---|---|---|
| Basic support | (Yes) | (Yes) | (Yes)[1] | (Yes) | (Yes) | (Yes) |
[1] Starting in Gecko 13.0 (Firefox 13.0 / Thunderbird 13.0 / SeaMonkey 2.10), null is always returned instead of the empty string, as per the DOM4 specification. Previously, there were cases in which an empty string could be returned.