Not a number (Definition)

A special numeric value used to handle computational error conditions.


ECMAScript edition - 2
Property/method value type:Number primitive

IEEE 754 describes a numeric regime that includes the ability to flag exceptions when calculations generate invalid results. The result of such an expression may be signified by the NaN or Not a Number exception.

See also:IEEE 754, NaN


ECMA 262 edition 2 - section - 4.3.23

ECMA 262 edition 3 - section - 4.3.23