org.w3c.dom

## Interface NamedNodeMap

-     public interface NamedNodeMap

  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.

  See also the Document Object Model (DOM) Level 3 Core Specification.

- - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `int` | `getLength()` The number of nodes in this map.
    `Node` | `getNamedItem(String name)` Retrieves a node specified by name.
    `Node` | `getNamedItemNS(String namespaceURI, String localName)` Retrieves a node specified by local name and namespace URI.
    `Node` | `item(int index)` Returns the `index`th item in the map.
    `Node` | `removeNamedItem(String name)` Removes a node specified by name.
    `Node` | `removeNamedItemNS(String namespaceURI, String localName)` Removes a node specified by local name and namespace URI.
    `Node` | `setNamedItem(Node arg)` Adds a node using its `nodeName` attribute.
    `Node` | `setNamedItemNS(Node arg)` Adds a node using its `namespaceURI` and `localName`.

- - ### Method Detail

    - #### getNamedItem

          Node getNamedItem(String name)

      Retrieves a node specified by name.
      Parameters:
        `name` - The `nodeName` of a node to retrieve.
      Returns:
        A `Node` (of any type) with the specified `nodeName`, or `null` if it does not identify any node in this map.

    - #### setNamedItem

          Node setNamedItem(Node arg)
                            throws DOMException

      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. Replacing a node by itself has no effect.
      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.
      Parameters:
        `arg` - A node to store in this map. The node will later be accessible using the value of its `nodeName` attribute.
      Returns:
        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.
        HIERARCHY_REQUEST_ERR: Raised if an attempt is made to add a node doesn't belong in this NamedNodeMap. Examples would include trying to insert something other than an Attr node into an Element's map of attributes, or a non-Entity node into the DocumentType's map of Entities.

    - #### removeNamedItem

          Node removeNamedItem(String name)
                               throws DOMException

      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.
      Parameters:
        `name` - The `nodeName` of the node to remove.
      Returns:
        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.

    - #### item

          Node item(int index)

      Returns the `index`th item in the map. If `index` is greater than or equal to the number of nodes in this map, this returns `null`.
      Parameters:
        `index` - Index into this map.
      Returns:
        The node at the `index`th position in the map, or `null` if that is not a valid index.

    - #### getLength

          int getLength()

      The number of nodes in this map. The range of valid child node indices is `0` to `length-1` inclusive.

    - #### getNamedItemNS

          Node getNamedItemNS(String namespaceURI,
                            String localName)
                              throws DOMException

      Retrieves a node specified by local name and namespace URI.
      Per [XML Namespaces] , applications must use the value null as the namespaceURI parameter for methods if they wish to have no namespace.
      Parameters:
        `namespaceURI` - The namespace URI of the node to retrieve.
        `localName` - The local name of the node to retrieve.
      Returns:
        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.
      Throws:
        `DOMException` - NOT_SUPPORTED_ERR: May be raised if the implementation does not support the feature "XML" and the language exposed through the Document does not support XML Namespaces (such as [HTML 4.01]).
      Since:
        DOM Level 2

    - #### setNamedItemNS

          Node setNamedItemNS(Node arg)
                              throws DOMException

      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. Replacing a node by itself has no effect.
      Per [XML Namespaces] , applications must use the value null as the namespaceURI parameter for methods if they wish to have no namespace.
      Parameters:
        `arg` - A node to store in this map. The node will later be accessible using the value of its `namespaceURI` and `localName` attributes.
      Returns:
        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.
        HIERARCHY_REQUEST_ERR: Raised if an attempt is made to add a node doesn't belong in this NamedNodeMap. Examples would include trying to insert something other than an Attr node into an Element's map of attributes, or a non-Entity node into the DocumentType's map of Entities.
        NOT_SUPPORTED_ERR: May be raised if the implementation does not support the feature "XML" and the language exposed through the Document does not support XML Namespaces (such as [HTML 4.01]).
      Since:
        DOM Level 2

    - #### removeNamedItemNS

          Node removeNamedItemNS(String namespaceURI,
                               String localName)
                                 throws DOMException

      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.
      Per [XML Namespaces] , applications must use the value null as the namespaceURI parameter for methods if they wish to have no namespace.
      Parameters:
        `namespaceURI` - The namespace URI of the node to remove.
        `localName` - The local name of the node to remove.
      Returns:
        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.
        NOT_SUPPORTED_ERR: May be raised if the implementation does not support the feature "XML" and the language exposed through the Document does not support XML Namespaces (such as [HTML 4.01]).
      Since:
        DOM Level 2

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