# isnan
> Test if a double-precision floating-point numeric value is NaN.
## Usage
```javascript
var isnan = require( '@stdlib/math/base/assert/is-nan' );
```
#### isnan( x )
Tests if a double-precision floating-point `numeric` value is `NaN`.
```javascript
var bool = isnan( NaN );
// returns true
```
## Examples
```javascript
var isnan = require( '@stdlib/math/base/assert/is-nan' );
var bool = isnan( NaN );
// returns true
bool = isnan( 5.0 );
// returns false
```