Name
Number.NaN: the special not-a-number value — 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 as 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
property NaN instead of Number.NaN.
See Also
isNaN( ), NaN
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