operator
key of specified? data-attributes of attribute-reference? [numeric-expression]
The key of data-attributes
operator returns the "true" name of the data-attribute. This is most useful when
retrieving the real name of an data-attribute that is being referenced through an alias. The name is uppercased when
the SGML declaration specifies NAMECASE GENERAL YES
for the SGML document being
processed.
When key of
is applied to data-attributes
, the item indexer is required.