Name
Number.NaN: the special not-a-number value â 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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