The Attr interface represents an attribute in an Element object. Typically the allowable values for the attribute are defined in a document type definition.

Although Attr objects inherit the Node interface, they are not considered part of the document tree and hence the Node attributes parentNode, previousSibling, and nextSibling have a null value for them. In XML, where the value of an attribute can contain entity references, the child nodes of the Attr node provide a representation in which entity references are not expanded. These child nodes may be either Text or EntityReference nodes. Because the attribute type may be unknown, there are no tokenized attribute values.