Microsoft® JScript™ isNaN Method

Language Reference  Version 1

See Also                  Applies To

Description

Determines whether a value is the reserved value NaN (not a number).

Syntax

isNaN(numvalue)

The numvalue argument is the value to be tested against NaN.

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 could be compared to itself. If it compares as unequal it is NaN. This is because NaN is the only value which is not equal to itself.

Note that isNaN is totally useless for checking that input is numerical. It passes '', ' ' and null as being numerical. Instead test parseInt ( number )