JavaScript NaN Property

Definition and Usage

The NaN property is a special value representing Not-a-Number. This property is used to indicate a value is not a number. A number object may be set to this value to indicate that it is not really a number.
Tip: Use the isNaN() global function to see if a value is an NaN value.

Syntax

Number.NaN

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Example

<script type="text/javascript"> var Month=30; if (Month < 1 || Month > 12) { Month = Number.NaN; } document.write(Month); </script>

The output of the code above will be:

Nan