Simple i18n helpers

translations.ts

type Path<T, Key extends keyof any = keyof T> = Key extends keyof T
  ? T[Key] extends object
    ? T[Key] extends infer R
      ? `${Key & string}.${Path<R, keyof R>}` | `${Key & string}`
      : never
    : `${Key & string}`
  : never;

type Paths<T> = Path<T> extends string ? Path<T> : never;
function translation<T, P extends Paths<T>>(
  obj: T,
  path: P,
): P extends keyof T ? T[P] : never {
  const keys = path.split('.') as Array<keyof T>;
  let result: any = obj;

  for (const key of keys) {
    result = result[key];
  }

  return result;
}
const translations = {
  path: {
    to: {
      key: 'a string',
    },
  },
};
console.log(translation(translations, 'path.to')); // { key: 'a string' }
console.log(translation(translations, 'path.too')); // Error
console.log(translation(translations, 'path.to.invalidKey')); // Error
console.log(translation(translations, 'path.to.key')); // 'a string'