# Native Function
> [Regular expression][regexp] to match a native function.
## Usage
```javascript
var reNativeFunction = require( '@stdlib/regexp/native-function' );
```
#### reNativeFunction()
Returns a [regular expression][regexp] to match a native `function`.
```javascript
var RE_NATIVE_FUNCTION = reNativeFunction();
var bool = RE_NATIVE_FUNCTION.test( Date.toString() );
// returns true
```
#### reNativeFunction.REGEXP
[Regular expression][regexp] to match a native `function`.
```javascript
var bool = reNativeFunction.REGEXP.test( Date.toString() );
// returns true
```
## Examples
```javascript
var Int8Array = require( '@stdlib/array/int8' );
var reNativeFunction = require( '@stdlib/regexp/native-function' );
var RE_NATIVE_FUNCTION = reNativeFunction();
function isNativeFunction( fcn ) {
return RE_NATIVE_FUNCTION.test( fcn.toString() );
}
var bool = isNativeFunction( Math.sqrt );
// returns true
bool = isNativeFunction( String );
// returns true
bool = isNativeFunction( Int8Array );
// returns true
bool = isNativeFunction( Date );
// returns true
bool = isNativeFunction( function noop() {} );
// returns false
```
[regexp]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Regular_Expressions