Deep Pick

deep-pick.ts

export const deepPick = <T extends object>(value: T) => {
  return <K extends keyof T & string>(path: K) => {
    return path.split('.').reduce<T[K]>((prev, curr) => {
      return typeof prev[curr] === 'object' ? prev[curr] : prev;
    }, value as T[K]);
  };
};

export function deep<T extends object>(value: T) {
  // prettier-ignore
  function pick<K extends keyof T & string, K2 extends keyof T[K] & string, K3 extends keyof T[K][K2] & string, K4 extends keyof T[K][K2][K3] & string>(path: `${K}.${K2}.${K3}.${K4}`): T[K][K2][K3]
  // prettier-ignore
  function pick<K extends keyof T & string, K2 extends keyof T[K] & string, K3 extends keyof T[K][K2] & string>(path: `${K}.${K2}.${K3}`): T[K][K2][K3]
  // prettier-ignore
  function pick<K extends keyof T & string, K2 extends keyof T[K] & string>(path: `${K}.${K2}`): T[K][K2]
  // prettier-ignore
  function pick<K extends keyof T & string>(path: K): T[K]
  function pick<K extends keyof T & string>(...path: K[]) {
    return path
      .join()
      .split('.')
      .reduce<T[K]>((prev, curr) => {
        return typeof prev[curr] === 'object' ? prev[curr] : prev;
      }, value as T[K]);
  }

  return pick;
}

const pick = deep({ a: { b: { c: 'gui' } } });

pick('a.b.c');