Function flatMap

flatMap<T, R>(
map: (value: T, index: number) => Iterable<R>,
): (values: Iterable<T>) => Generator<R>
Creates a generator that maps each element in an iterable to another iterable, then flattens the results into a single generator. Similar to Array.prototype.flatMap(), but works with any iterable.
Type Parameters
- T
  Type of elements in the input iterable
- R
  Type of elements in the resulting generator
Parameters
- map: (value: T, index: number) => Iterable<R>
  Function that maps each value to an iterable of new values
Returns (values: Iterable<T>) => Generator<R>
A function that takes an iterable and returns a flattened generator
Yields
Values from all mapped iterables in sequence
Example
```
// Expand each number into an array of that many elements
const expanded = [...flatMap((n: number) => Array(n).fill(n))([1, 2, 3])]
// Result: [1, 2, 2, 3, 3, 3]
```
Example
```
// Map words to their characters
const chars = [...flatMap((word: string) => word)(['hello', 'world'])]
// Result: ['h', 'e', 'l', 'l', 'o', 'w', 'o', 'r', 'l', 'd']
```
Example
```
// With index
const withIndices = [...flatMap((n: number, i: number) => [n, i])([10, 20, 30])]
// Result: [10, 0, 20, 1, 30, 2]
```
- Defined in generator/src/flat-map.ts:28