# broadcastArrays
> Broadcast [ndarrays][@stdlib/ndarray/ctor] to a common shape.
## Usage
```javascript
var broadcastArrays = require( '@stdlib/ndarray/broadcast-arrays' );
```
#### broadcastArrays( ...arrays )
Broadcasts a list of [ndarrays][@stdlib/ndarray/ctor] to a common shape.
```javascript
var array = require( '@stdlib/ndarray/array' );
var zeros = require( '@stdlib/ndarray/zeros' );
// Create a 2x2 ndarray:
var x = array( [ [ 1, 2 ], [ 3, 4 ] ] );
// returns
// Create a 2x2x2 ndarray:
var y = zeros( [ 2, 2, 2 ] );
// returns
// Broadcast to a common shape:
var out = broadcastArrays( [ x, y ] );
// returns [ , ]
```
The function supports two (mutually exclusive) means for providing [ndarray][@stdlib/ndarray/ctor] arguments:
1. providing a single array of [ndarray][@stdlib/ndarray/ctor] arguments.
2. providing [ndarray][@stdlib/ndarray/ctor] arguments as separate arguments.
```javascript
var array = require( '@stdlib/ndarray/array' );
var zeros = require( '@stdlib/ndarray/zeros' );
// Create a 2x2 ndarray:
var x = array( [ [ 1, 2 ], [ 3, 4 ] ] );
// returns
// Create a 2x2x2 ndarray:
var y = zeros( [ 2, 2, 2 ] );
// returns
// Broadcast to a common shape:
var out = broadcastArrays( x, y );
// returns [ , ]
```
## Notes
- The function throws an error if provided [broadcast-incompatible][@stdlib/ndarray/base/broadcast-shapes] ndarrays.
- Returned [ndarrays][@stdlib/ndarray/ctor] are **read-only** views on their respective underlying data buffers. The views are typically **not** contiguous. As more than one element of a returned view may refer to the same memory location, writing to a view may affect multiple elements. If you need to write to a returned [ndarray][@stdlib/ndarray/ctor], copy the [ndarray][@stdlib/ndarray/ctor] **before** broadcasting.
- The function always returns new [ndarray][@stdlib/ndarray/ctor] instances even if an input [ndarray][@stdlib/ndarray/ctor] shape and the broadcasted shape are the same.
## Examples
```javascript
var array = require( '@stdlib/ndarray/array' );
var zeros = require( '@stdlib/ndarray/zeros' );
var numel = require( '@stdlib/ndarray/base/numel' );
var ind2sub = require( '@stdlib/ndarray/ind2sub' );
var broadcastArrays = require( '@stdlib/ndarray/broadcast-arrays' );
// Create a 2x2 array:
var x = array( [ [ 1, 2 ], [ 3, 4 ] ] );
// returns
// Create a 3x2x2 array:
var y = zeros( [ 3, 2, 2 ] );
// returns
// Broadcast the arrays to a common shape:
var out = broadcastArrays( [ x, y ] );
// returns [ , ]
// Retrieve the common shape:
var sh = out[ 0 ].shape;
// returns [ 3, 2, 2 ]
// Retrieve the number of elements:
var N = numel( sh );
// Loop through the array elements...
var i;
for ( i = 0; i < N; i++ ) {
console.log( 'X[%s] = %d', ind2sub( sh, i ).join( ', ' ), out[ 0 ].iget( i ) );
}
```
[@stdlib/ndarray/ctor]: https://github.com/stdlib-js/ndarray/tree/main/ctor
[@stdlib/ndarray/base/broadcast-shapes]: https://github.com/stdlib-js/ndarray/tree/main/base/broadcast-shapes
[@stdlib/ndarray/array]: https://github.com/stdlib-js/ndarray/tree/main/array
[@stdlib/ndarray/broadcast-array]: https://github.com/stdlib-js/ndarray/tree/main/broadcast-array
[@stdlib/ndarray/maybe-broadcast-arrays]: https://github.com/stdlib-js/ndarray/tree/main/maybe-broadcast-arrays