Attr - Web APIs
ownerelement read only the element holding the attribute.
... living standard added ownerelement property back dom4the definition of 'attr' in that specification.
... obsolete moved namespaceuri, prefix and localname from node to this api and removed ownerelement, schematypeinfo and isid.

IsDefaultNamespace - Archive of obsolete content
return false; // unknown; } case 9: // document_node return isdefaultnamespace(node.documentelement, namespaceuri); case 6: // entity_node case 12: // notation_node case 10: // document_type_node case 11: // document_fragment_node return false; // unknown case 2: // attribute_node: if (node.ownerelement ) { return isdefaultnamespace(node.ownerelement , namespaceuri); } else { return false; // unknown } default: if (node.parentnode) { // entityreferences may have to be skipped to get to it return isdefaultnamespace(node.parentnode, namespaceuri); } else { ...

LookupNamespaceURI - Archive of obsolete content
return null; case 9: // document_node return lookupnamespaceurihelper(node.documentelement, prefix); case 6: // entity_node case 12: // notation_node case 10: // document_type_node case 11: // document_fragment_node return null; // unknown case 2: // attribute_node if (node.ownerelement) { return lookupnamespaceurihelper(node.ownerelement, prefix); } return null; // unknown default: // text_node (3), cdata_section_node (4), entity_reference_node (5), // processing_instruction_node (7), comment_node (8) if (node.parentnode) { // entityreferences may have...

LookupPrefix - Archive of obsolete content
/ node.element_node return _lookupnamespaceprefix(namespaceuri, node); case 9: // node.document_node return _lookupnamespaceprefix(namespaceuri, node.documentelement); case 6: // node.entity_node case 12: // node.notation_node case 11: // node.document_fragment_node case 10: // node.document_type_node return null; // type is unknown case 2: // node.attribute_node if (node.ownerelement) { return _lookupnamespaceprefix(namespaceuri, node.ownerelement); } return null; default: if (node.parentnode) { // entityreferences may have to be skipped to get to it return _lookupnamespaceprefix(namespaceuri, node.parentnode); } return null; } } // private function for lookupprefix only function _lookupnamespaceprefix (namespaceuri, originalelement) { var xml...

Element.getAttributeNode() - Web APIs
you can, however, get the element to which the attribute belongs with the ownerelement property.