# promoteDataTypes
> Resolve the data type that results from applying [promotion rules][@stdlib/ndarray/promotion-rules] to a provided list of data types.
## Usage
```javascript
var promoteDataTypes = require( '@stdlib/ndarray/base/promote-dtypes' );
```
#### promoteDataTypes( dtypes )
Returns a data type that results from applying [promotion rules][@stdlib/ndarray/promotion-rules] to a provided list of data types.
```javascript
var dt = promoteDataTypes( [ 'float32', 'float64' ] );
// returns 'float64'
```
The function returns `null` if provided data types which cannot be safely cast to a promoted data type.
```javascript
var dt = promoteDataTypes( [ 'binary', 'complex128' ] );
// returns null
```
## Examples
```javascript
var dtypes = require( '@stdlib/ndarray/dtypes' );
var cartesianProduct = require( '@stdlib/array/base/cartesian-product' );
var logEachMap = require( '@stdlib/console/log-each-map' );
var promoteDataTypes = require( '@stdlib/ndarray/base/promote-dtypes' );
// Get the list of supported data types:
var dt = dtypes();
// Generate data type pairs:
var pairs = cartesianProduct( dt, dt );
// Resolve promoted data types:
logEachMap( '(%s) => %s', pairs, promoteDataTypes );
```
[@stdlib/ndarray/promotion-rules]: https://github.com/stdlib-js/ndarray/tree/main/promotion-rules