KeyPath.ts

export class KeyPath<T extends string = string> {
  #_brand!: never;

  readonly #path: readonly string[];

  constructor(path: T) {
    this.#path = path.split(".");
  }

  of<Expected>(object: unknown): Expected {
    for (const key of this.#path) {
      if (object == null) {
        break;
      }

      object = (object as Record<string, unknown>)[key];
    }

    return object as Expected;
  }
}