Number.NaN |
the special not-a-number value |
Availability
JavaScript 1.1; JScript 2.0, ECMAScript v1
Synopsis
Number.NaN
Description
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
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