是自己寫的，只不過老師直接復制過來了

const?STORAGE_KEY?=?'todos_vuejs';
export?default?{
????fetch()?{
????????return?JSON.parse(window.localStorage.getItem(STORAGE_KEY?||?'[]'));
????},
????save(items)?{
????????window.localStorage.setItem(STORAGE_KEY,?JSON.stringify(items));
????}
}