add_action('wp_body_open', 'mtnb_skeleton');
function mtnb_skeleton() {
    echo '
';
}

add_action('wp_enqueue_scripts', 'mtnb_assets');
function mtnb_assets() {
    wp_enqueue_style('mtnb-css', plugins_url('topbar.css', __FILE__));
    wp_enqueue_script('mtnb-js', plugins_url('topbar.js', __FILE__), 【】, false, true);
}

document.addEventListener('DOMContentLoaded', () => {
    const root = document.getElementById('mtnb-root');
    root.innerHTML = '限时优惠：全场插件8折！×';
    root.classList.add('active');
    document.getElementById('mtnb-close').onclick = () => root.style.height='0';
});