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Element.getAttributeNS() - Web APIs 编辑

The getAttributeNS() method of the Element interface 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.

Note: Earlier versions of the DOM specification had this method described as returning an empty string for non-existent attributes, but it was not typically implemented this way since null makes more sense. The DOM4 specification now says this method should return null for non-existent attributes.

Examples

The following SVG document reads the value of the foo attribute in a custom namespace.

<svg xmlns="http://www.w3.org/2000/svg"
    xmlns:test="http://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 = 'http://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="http://www.w3.org/2000/svg"
    xmlns:test="http://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 = 'http://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.	Obsolete	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.	Obsolete	Initial definition

Browser compatibility

BCD tables only load in the browser

Element.getAttributeNS() - Web APIs 编辑

Syntax

Parameters

Return value

Examples

Notes

Specifications

Browser compatibility

See also

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Element.getAttributeNS() - Web APIs 编辑

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