mathjs/docs/reference/functions/isNaN.md

Math.js is an extensive math library for JavaScript and Node.js. It features a flexible expression parser and offers an integrated solution to work with numbers, big numbers, complex numbers, units, and matrices.

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# 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 &#124; BigNumber &#124; Fraction &#124; Unit &#124; Array &#124; 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)