TypeScript: `keyof` и `typeof` — пример кода

// A getter that's provably safe against typos
function pluck<T, K extends keyof T>(obj: T, key: K): T[K] {
  return obj[key];
}
const user = { id: 1, name: 'Ada' };
pluck(user, 'name');              // string
// pluck(user, 'nope');           // ❌ 'nope' is not keyof typeof user

// Turn a const object into a single source of truth
const STATUS = { active: 1, archived: 2 } as const;
type StatusKey = keyof typeof STATUS;         // 'active' | 'archived'
type StatusCode = typeof STATUS[StatusKey];   // 1 | 2

// keyof an index signature is WIDER than you expect
type Dict = { [k: string]: number };
type DictKeys = keyof Dict;       // string | number  (not just string!)