The Attr interface represents an attribute in an Element object. Typically the allowable values for the attribute are defined in a document type definition.
The attribute's effective value is determined as follows: if this attribute has been explicitly assigned any value, that value is the attribute's effective value; otherwise, if there is a declaration for this attribute, and that declaration includes a default value, then that default value is the attribute's effective value; otherwise, the attribute does not exist on this element in the structure model until it has been explicitly added. Note that the Node.nodeValue attribute on the Attr instance can also be used to retrieve the string version of the attribute's value(s).
In XML, where the value of an attribute can contain entity references, the child nodes of the Attr node may be either Text or EntityReference nodes. Because the DOM Core is not aware of attribute types, it treats all attribute values as simple strings, even if the DTD or schema declares them as having tokenized types.
Note that this object is implemented and supported by the web browser and results of its use may vary.
If this attribute was explicitly given a value in the original document, this is true; otherwise, it is false. Note that the implementation is in charge of this attribute, not the user. If the user changes the value of the attribute (even if it ends up having the same value as the default value) then the specified flag is automatically flipped to true. To re-specify the attribute as the default value from the DTD, the user must delete the attribute. The implementation will then make a new attribute available with specified set to false and the default value (if one exists). In summary:
If the attribute has an assigned value in the document then specified is true , and the value is the assigned value.
If the attribute has no assigned value in the document and has a default value in the DTD, then specified is false , and the value is the default value in the DTD.
If the attribute has no assigned value in the document and has a value of #IMPLIED in the DTD, then the attribute does not appear in the structure model of the document.
If the ownerElement attribute is null (i.e. because it was just created or was set to null by the various removal and cloning operations) specifiedis true .
On retrieval, the value of the attribute is returned as a string. Character and general entity references are replaced with their values. See also the method "Element#getAttribute" on the Element interface.
On the Setting, this creates a Text node with the unparsed contents of the string. I.e. any characters that an XML processor would recognize as markup are instead treated as literal text. See also the method "Element#setAttribute" on the Element interface.