indexed-collection/src/core/KeyExtract.ts

A zero-dependency library of classes that make filtering, sorting and observing changes to arrays easier and more efficient.

/**
 * Delegate for extracting key from the given item
 */
export type KeyExtract<T = unknown, KeyT = unknown> = SingleKeyExtract<T, KeyT> | MultipleKeyExtract<T, KeyT>;

export type SingleKeyExtract<T = unknown, KeyT = unknown> = {
  isMultiple?: boolean;
  (item: T): KeyT;
};

export type MultipleKeyExtract<T = unknown, KeyT = unknown> = {
  isMultiple: true;
  (item: T): readonly KeyT[] | ReadonlySet<KeyT>;
};