FOM 参考 > DOM Support > DOM > NamedNodeMap interface
NamedNodeMap interface
Objects implementing the NamedNodeMap interface are used to represent collections of nodes that can be accessed by name. Note that NamedNodeMap does not inherit from NodeList; NamedNodeMaps are not maintained in any particular order. Objects contained in an object implementing NamedNodeMap may also be accessed by an ordinal index, but this is simply to allow convenient enumeration of the contents of a NamedNodeMap, and does not imply that the DOM specifies an order to these Nodes.
NamedNodeMap objects in the DOM are live.
length attribute
The number of nodes in this map. The range of valid child node indices is 0 to length-1 inclusive.
length
Access
read-only
Returns
unsigned long
getNamedItem method
Retrieves a node specified by name.
getNamedItem name
Parameters
String name
The nodeName of a node to retrieve.
Returns
Node. A Node (of any type) with the specified nodeName, or null if it does not identify any node in this map.
getNamedItemNS method
Retrieves a node specified by local name and namespace URI. HTML-only DOM implementations do not need to implement this method.
getNamedItemNS namespaceURI localName
Parameters
String namespaceURI
The namespace URI of the node to retrieve.
String localName
The local name of the node to retrieve.
Returns
Node. A Node (of any type) with the specified local name and namespace URI, or null if they do not identify any node in this map.
item method
Returns the indexth item in the map. If index is greater than or equal to the number of nodes in this map, this returns null.
item nodeindex
Parameters
unsigned long nodeindex
Index into this map.
Returns
Node. The node at the indexth position in the map, or null if that is not a valid index.
namedItem method
Retrieves a node specified by name.
namedItem name
Parameters
String name
The nodeName of a node to retrieve.
Returns
Node. A Node (of any type) with the specified nodeName, or null if it does not identify any node in this map.
removeNamedItem method
Removes a node specified by name. When this map contains the attributes attached to an element, if the removed attribute is known to have a default value, an attribute immediately appears containing the default value as well as the corresponding namespace URI, local name, and prefix when applicable.
removeNamedItem name
Parameters
String name
The nodeName of the node to remove.
Returns
Node. The node removed from this map if a node with such a name exists.
Throws
DOMException
NOT_FOUND_ERR: Raised if there is no node named name in this map.
NO_MODIFICATION_ALLOWED_ERR: Raised if this map is readonly.
removeNamedItemNS method
Removes a node specified by local name and namespace URI. A removed attribute may be known to have a default value when this map contains the attributes attached to an element, as returned by the attributes attribute of the Node interface. If so, an attribute immediately appears containing the default value as well as the corresponding namespace URI, local name, and prefix when applicable.
HTML-only DOM implementations do not need to implement this method.
removeNamedItemNS namespaceURI localName
Parameters
String namespaceURI
The namespace URI of the node to remove.
String localName
The local name of the node to remove.
Returns
Node. The node removed from this map if a node with such a local name and namespace URI exists.
Throws
DOMException
NOT_FOUND_ERR: Raised if there is no node with the specified namespaceURI and localName in this map.
NO_MODIFICATION_ALLOWED_ERR: Raised if this map is readonly.
setNamedItem method
Adds a node using its nodeName attribute. If a node with that name is already present in this map, it is replaced by the new one.
As the nodeName attribute is used to derive the name which the node must be stored under, multiple nodes of certain types (those that have a "special" string value) cannot be stored as the names would clash. This is seen as preferable to allowing nodes to be aliased.
setNamedItem arg
Parameters
Node arg
A node to store in this map. The node will later be accessible using the value of its nodeName attribute.
Returns
Node. If the new Node replaces an existing node the replaced Node is returned, otherwise null is returned.
Throws
DOMException
WRONG_DOCUMENT_ERR: Raised if arg was created from a different document than the one that created this map.
NO_MODIFICATION_ALLOWED_ERR: Raised if this map is readonly.
INUSE_ATTRIBUTE_ERR: Raised if arg is an Attr that is already an attribute of another Element object. The DOM user must explicitly clone Attr nodes to re-use them in other elements.
setNamedItemNS method
Adds a node using its namespaceURI and localName. If a node with that namespace URI and that local name is already present in this map, it is replaced by the new one.
HTML-only DOM implementations do not need to implement this method.
setNamedItemNS arg
Parameters
Node arg
A node to store in this map. The node will later be accessible using the value of its namespaceURI and localName attributes.
Returns
Node. If the new Node replaces an existing node the replaced Node is returned, otherwise null is returned.
Throws
DOMException
WRONG_DOCUMENT_ERR: Raised if arg was created from a different document than the one that created this map.
NO_MODIFICATION_ALLOWED_ERR: Raised if this map is readonly.
INUSE_ATTRIBUTE_ERR: Raised if arg is an Attr that is already an attribute of another Element object. The DOM user must explicitly clone Attr nodes to re-use them in other elements.
Parent topic 
DOM
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