# Function isNaN Test whether a value is NaN (not a number). The function supports types `number`, `BigNumber`, `Fraction`, `Unit` and `Complex`. The function is evaluated element-wise in case of Array or Matrix input. ## Syntax ```js math.isNaN(x) ``` ### Parameters Parameter | Type | Description --------- | ---- | ----------- `x` | number | BigNumber | Fraction | Unit | Array | Matrix | Value to be tested ### Returns Type | Description ---- | ----------- boolean | Returns true when `x` is NaN. Throws an error in case of an unknown data type. ## Examples ```js math.isNaN(3) // returns false math.isNaN(NaN) // returns true math.isNaN(0) // returns false math.isNaN(math.bignumber(NaN)) // returns true math.isNaN(math.bignumber(0)) // returns false math.isNaN(math.fraction(-2, 5)) // returns false math.isNaN('-2') // returns false math.isNaN([2, 0, -3, NaN]') // returns [false, false, false, true] ``` ## See also [isNumeric](isNumeric.md), [isNegative](isNegative.md), [isPositive](isPositive.md), [isZero](isZero.md), [isInteger](isInteger.md)