truewhen the attribute has a value, and
isntreverses the result.
attribute attribute-name (of element-expression)? (is | isnt) specified
is specified attribute type test succeeds when:
The test fails otherwise. Using
isnt instead of
is reverses the results.
Unlike all other attribute references, no error occurs if the specified attribute does not exist, or was not given a value, since the test does not actually use the value.
If the element-expression references an element that does not exist, or if the specified
attribute is not declared, the
is form of the test always fails, and the