Or not goofy, if you think of 'number' as an enum constant denoting that variable's type, rather than its value. In this context, 'NaN' just happens to be anot

Or not goofy, if you think of 'number' as an enum constant denoting that variable's type, rather than its value. In this context, 'NaN' just happens to be another admissible value within the space of "number".