The following number constants are properties of the Number object.
You do not have to create Number object to access these constants.
A value that is not a number.
In equality comparisons, NaN does not equal any value, including itself. To test whether a value is equivalent to NaN, use the isNaN function.
Supported in the following document modes: Quirks, Internet Explorer 6 standards, Internet Explorer 7 standards, Internet Explorer 8 standards, Internet Explorer 9 standards, Internet Explorer 10 standards, Internet Explorer 11 standards. Also supported Store apps (Windows 8 and Windows Phone 8.1). See Version Information.