TS match functions

match.ts

type Key = string | number | symbol;

type ExhaustiveMatch<K extends Key, T> = Record<K, T>;
type PartialMatch<K extends Key, T> = Partial<Record<K, T>> & { _: T };

export const match = <T, K extends Key = Key>(
  key: K,
  map: ExhaustiveMatch<K, T> | PartialMatch<K, T>,
): T => (map.hasOwnProperty(key) ? map[key] : (map as PartialMatch<K, T>)._) as T;

export const lazymatch = <T, K extends Key = Key>(
  key: K,
  map: ExhaustiveMatch<K, () => T> | PartialMatch<K, () => T>,
): T => ((map.hasOwnProperty(key) ? map[key] : (map as PartialMatch<K, () => T>)._) as () => T)();