function dtypeEnum( arr ) {
	var dt = dtype( arr );
	if ( dt ) {
		return str2enum( dt );
	}
	return null;
}
Returns the data type enumeration constant for a provided ndarray data buffer.

@param {Collection} arr - strided array
@returns {(integer|null)} data type enumeration constant or null

@example
var Float64Array = require( '@stdlib/array/float64' );

var x = new Float64Array( 10 );

var c = dtypeEnum( x );
// returns <number>