Function mapBy

mapBy<T, K extends string | number, I = T>(
    iterable: Iterable<T>,
    keySelector: keyof T | ((item: T, index: number) => undefined | K),
    itemSelector?: (item: T, index: number) => I,
): Map<K, I>
Creates a Map of an iterable object mapping each item to the specified key. The key can be a property name or a function. If the key is not unique the last item will be used that matches the key.
Type Parameters
- T
- K extends string | number
- I = T
Parameters
- iterable: Iterable<T>
  iterable items to map
- keySelector: keyof T | ((item: T, index: number) => undefined | K)
  function to get the map by key
- OptionalitemSelector: (item: T, index: number) => I
  function to get the the item value; defaults to the items being iterated
Returns Map<K, I>
- Defined in packages/util/src/collection.ts:220