class CustomFooter extends HTMLElement { connectedCallback() { this.attachShadow({ mode: 'open' }); this.shadowRoot.innerHTML = ` `; const updateDateEl = this.shadowRoot.getElementById('updateDate'); const now = new Date(); updateDateEl.textContent = now.toLocaleDateString('zh-CN', { year: 'numeric', month: 'long', day: 'numeric' }); } } customElements.define('custom-footer', CustomFooter);