# iterForEach
> Create an iterator which invokes a function for each iterated value before returning the iterated value.
## Usage
```javascript
var iterForEach = require( '@stdlib/iter/for-each' );
```
#### iterForEach( iterator, fcn\[, thisArg] )
Returns an iterator which invokes a `function` for each iterated value **before** returning the iterated value.
```javascript
var array2iterator = require( '@stdlib/array/to-iterator' );
function assert( v ) {
if ( v !== v ) {
throw new Error( 'should not be NaN' );
}
}
var it = iterForEach( array2iterator( [ 1, 2, 3, 4 ] ), assert );
// returns
## Notes
- If an environment supports `Symbol.iterator` **and** a provided iterator is iterable, the returned iterator is iterable.
## Examples
```javascript
var randu = require( '@stdlib/random/iter/randu' );
var isnan = require( '@stdlib/math/base/assert/is-nan' );
var iterForEach = require( '@stdlib/iter/for-each' );
function assert( v ) {
if ( isnan( v ) ) {
throw new Error( 'should not be NaN' );
}
}
// Create a seeded iterator for generating pseudorandom numbers:
var rand = randu({
'seed': 1234,
'iter': 10
});
// Create an iterator which validates generated numbers:
var it = iterForEach( rand, assert );
// Perform manual iteration...
var r;
while ( true ) {
r = it.next();
if ( r.done ) {
break;
}
console.log( r.value );
}
```
* * *
## See Also
- [`@stdlib/iter/map`][@stdlib/iter/map]: create an iterator which invokes a function for each iterated value.
[@stdlib/iter/map]: https://github.com/stdlib-js/iter/tree/main/map