localStorageは保存されていません。
<button id="b">名前・年齢の入力ボタン</button> <p id="r">localStorageは保存されていません。</p>
const setStorage = (key, value, expire) => { let data; if (expire !== undefined) { data = { expire: expire, value: value }; } else { data = value; } localStorage.setItem(key, JSON.stringify(data)); } const getStorage = (key) => { let s = localStorage[key]; if (s === undefined) { return undefined; } s = JSON.parse(s); if (new Date(s.expire) > new Date()) { return s.value; } else { localStorage.removeItem(key); return undefined; } } const b = document.getElementById('b'); b.addEventListener('click', () => { const n = prompt('Input your name.', ''); const a = prompt('Input your age.', ''); const data = { name: n, age: a }; setStorage('test', data, '2050/01/01 00:00'); r.textContent = getStorage('test').name + ' ' + getStorage('test').age; }); if (getStorage('test')) { const r = document.getElementById('r'); r.textContent = getStorage('test').name + ' ' + getStorage('test').age; }