# Buffer Data Type
> Return the data type of an ndarray data buffer.
## Usage
```javascript
var dtype = require( '@stdlib/ndarray/base/buffer-dtype' );
```
#### dtype( buffer )
Returns the [data type][@stdlib/ndarray/dtypes] of an ndarray data [buffer][@stdlib/ndarray/base/buffer-ctors].
```javascript
var Float64Array = require( '@stdlib/array/float64' );
var buf = new Float64Array( 10 );
var dt = dtype( buf );
// returns 'float64'
```
If provided an ndarray data [buffer][@stdlib/ndarray/base/buffer-ctors] having an unknown or unsupported [data type][@stdlib/ndarray/dtypes], the function returns `null`.
```javascript
var dt = dtype( 'beep' );
// returns null
```
## Examples
```javascript
var dtypes = require( '@stdlib/ndarray/dtypes' );
var bufferCtors = require( '@stdlib/ndarray/base/buffer-ctors' );
var dtype = require( '@stdlib/ndarray/base/buffer-dtype' );
// Get a list of supported ndarray buffer data types:
var DTYPES = dtypes( 'integer_and_generic' );
// Buffer length:
var len = 10;
// For each supported data type, create a buffer and confirm its data type...
var ctor;
var dt;
var i;
for ( i = 0; i < DTYPES.length; i++ ) {
ctor = bufferCtors( DTYPES[ i ] );
dt = dtype( new ctor( len ) );
console.log( '%s == %s => %s', DTYPES[ i ], dt, DTYPES[ i ] === dt );
}
// Try an array-like object...
var buf = {
'length': len
};
dt = dtype( buf );
console.log( '%s == %s => %s', 'generic', dt, dt === 'generic' );
```
[@stdlib/ndarray/dtypes]: https://github.com/stdlib-js/ndarray/tree/main/dtypes
[@stdlib/ndarray/base/buffer-ctors]: https://github.com/stdlib-js/ndarray/tree/main/base/buffer-ctors