localStorage 연산

const storage = {
  set(key, value, expire) {
    const data = { value, expire: expire ? Date.now() + expire : null };
    localStorage.setItem(key, JSON.stringify(data));
  },
  get(key) {
    const raw = localStorage.getItem(key);
    if (!raw) return null;
    const data = JSON.parse(raw);
    if (data.expire && Date.now() > data.expire) {
      localStorage.removeItem(key);
      return null;
    }
    return data.value;
  },
  remove(key) { localStorage.removeItem(key); }
};