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JavaScript: The Definitive Guide, 4th Edition
By
David Flanagan
Publisher
: O'Reilly
Pub Date
: November 2001
ISBN
: 0-596-00048-0
Pages
: 936
Slots
: 1
This fourth edition of the definitive reference to
JavaScript, a scripting language that can be embedded
directly in web pages, covers the latest version of the
language, JavaScript 1.5, as supported by Netscape 6 and
Internet Explorer 6. The book also provides complete
coverage of the W3C DOM standard (Level 1 and Level 2),
while retaining material on the legacy Level 0 DOM for
backward compatibility.
Availability
JavaScript 1.1; JScript 2.0, ECMAScript v1
Synopsis
Number.NaNDescription
Number.NaN is
a special value that indicates that the result of some mathematical
operation (such as taking the square root of a negative number) is
not a number. parseInt( ) and parseFloat(
) return this value when they cannot parse the specified
string, and you might use Number.NaN in a similar
way to indicate an error condition for some function that normally
returns a valid number.
JavaScript prints the Number.NaN value as
NaN. Note that the NaN value
always compares unequal to any other number, including
NaN itself. Thus, you cannot check for the
not-a-number value by comparing to Number.NaN. Use
the isNaN( ) function instead. In ECMAScript v1
and later, you can also use the predefined global constant
NaN instead of using
Number.NaN.
See Also
isNaN( ), NaN
