# forEach
> Invoke a callback function once for each [ndarray][@stdlib/ndarray/ctor] element.
## Usage
```javascript
var forEach = require( '@stdlib/ndarray/for-each' );
```
#### forEach( x, fcn\[, thisArg] )
Invokes a callback function once for each [ndarray][@stdlib/ndarray/ctor] element.
```javascript
var Float64Array = require( '@stdlib/array/float64' );
var ndarray = require( '@stdlib/ndarray/ctor' );
var naryFunction = require( '@stdlib/utils/nary-function' );
var log = require( '@stdlib/console/log' );
var buffer = new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0, 11.0, 12.0 ] );
var shape = [ 2, 3 ];
var strides = [ 6, 1 ];
var offset = 1;
var x = ndarray( 'float64', buffer, shape, strides, offset, 'row-major' );
// returns
forEach( x, naryFunction( log, 1 ) );
```
The function accepts the following arguments:
- **x**: input [ndarray][@stdlib/ndarray/ctor].
- **fcn**: callback to apply.
- **thisArg**: callback execution context _(optional)_.
To set the callback function execution context, provide a `thisArg`.
```javascript
var Float64Array = require( '@stdlib/array/float64' );
var ndarray = require( '@stdlib/ndarray/ctor' );
function accumulate( z ) {
this.sum += z;
}
var buffer = new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0, 11.0, 12.0 ] );
var shape = [ 2, 3 ];
var strides = [ 6, 1 ];
var offset = 1;
var x = ndarray( 'float64', buffer, shape, strides, offset, 'row-major' );
// returns
var ctx = {
'sum': 0
};
forEach( x, accumulate, ctx );
var sum = ctx.sum;
// returns 36
```
The callback function is provided the following arguments:
- **value**: current array element.
- **indices**: current array element indices.
- **arr**: the input [ndarray][@stdlib/ndarray/ctor].
## Notes
- For very high-dimensional ndarrays which are non-contiguous, one should consider copying the underlying data to contiguous memory before applying a callback function in order to achieve better performance.
## Examples
```javascript
var discreteUniform = require( '@stdlib/random/array/discrete-uniform' );
var ndarray = require( '@stdlib/ndarray/ctor' );
var ndarray2array = require( '@stdlib/ndarray/to-array' );
var naryFunction = require( '@stdlib/utils/nary-function' );
var log = require( '@stdlib/console/log' );
var forEach = require( '@stdlib/ndarray/for-each' );
var buffer = discreteUniform( 10, -100, 100, {
'dtype': 'generic'
});
var shape = [ 5, 2 ];
var strides = [ 2, 1 ];
var offset = 0;
var x = ndarray( 'generic', buffer, shape, strides, offset, 'row-major' );
log( ndarray2array( x ) );
forEach( x, naryFunction( log, 2 ) );
```
[@stdlib/ndarray/ctor]: https://github.com/stdlib-js/ndarray/tree/main/ctor
[@stdlib/ndarray/map]: https://github.com/stdlib-js/ndarray/tree/main/map