isNaN Method

Returns a Boolean value that indicates whether a value is the reserved value NaN (not a number).

function isNaN(number : Number) : Boolean

Arguments

• number
  Required. A numeric value.

Remarks

The isNaN function returns true if the value is NaN, and false otherwise. You typically use this function to test return values from the parseInt and parseFloat methods.

Alternatively, a variable that contains NaN or another value could be compared to itself. If it compares as unequal, it is NaN. This is because NaN is the only value that is not equal to itself.

Requirements

Version 1

Applies To:

Global Object

Example

// Returns false.
isNaN(100);
// Returns false.
isNaN("100");
// Returns true.
isNaN("ABC");
// Returns true.
isNaN("10C");
// Returns true.
isNaN(Math.sqrt(-1));

See Also

Reference

isFinite Method

NaN Property (Global)

parseFloat Method

parseInt Method

Change History

Date	History	Reason
March 2009	Added example and clarified information in the Remarks section.	Information enhancement.