Function selectMany

selectMany<TElement, TResult>(
source: Iterable<TElement>,
selector: IndexedSelector<TElement, Iterable<TResult, any, any>>,
): IEnumerable<TResult>
Projects each element and index into an iterable and flattens the results into a single sequence.
Type Parameters
- TElement
  Type of elements within the source iterable.
- TResult
  Element type produced by the flattened iterables.
Parameters
- source: Iterable<TElement>
  The source iterable.
- selector: IndexedSelector<TElement, Iterable<TResult, any, any>>
  Projection that returns an iterable for each element and its index.
Returns IEnumerable<TResult>
A deferred sequence containing the concatenated contents of the iterables produced by selector.
Remarks
Each inner iterable is fully enumerated in order before the next source element is processed, preserving the relative ordering of results.
Example
```
const lists = [[1, 2], [3, 4], [5]];
const flattened = selectMany(lists, x => x).toArray();
console.log(flattened); // [1, 2, 3, 4, 5]
```
- Defined in src/enumerator/functions/selectMany.ts:20