isNAN

Description

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

Syntax

isNaN(value)

Parameters

value

The value to be tested against NaN.

Returns

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 that is not equal to itself.