Accessible mega-menu nav walker

<?php
/**
 * Navigation walker with disclosure buttons.
 *
 * @package Acme_Theme
 */

defined( 'ABSPATH' ) || exit;

class Acme_Mega_Walker extends Walker_Nav_Menu {

	public function start_lvl( &$output, $depth = 0, $args = null ) {
		$output .= '<ul class="acme-panel acme-panel--depth-' . (int) ( $depth + 1 ) . '" hidden>';
	}

	public function start_el( &$output, $data_object, $depth = 0, $args = null, $current_object_id = 0 ) {
		$item       = $data_object;
		$has_kids   = in_array( 'menu-item-has-children', (array) $item->classes, true );
		$is_current = in_array( 'current-menu-item', (array) $item->classes, true );

		$output .= '<li class="acme-item' . ( $has_kids ? ' has-panel' : '' ) . '">';

		$output .= sprintf(
			'<a href="%1$s"%2$s>%3$s</a>',
			esc_url( $item->url ),
			$is_current ? ' aria-current="page"' : '',
			esc_html( $item->title )
		);

		if ( $has_kids ) {
			$output .= sprintf(
				'<button type="button" class="acme-disclose" aria-expanded="false" aria-label="%s"></button>',
				/* translators: %s: menu item title */
				esc_attr( sprintf( __( 'Toggle submenu for %s', 'acme-theme' ), $item->title ) )
			);
		}
	}
}

// Usage:
// wp_nav_menu( array( 'theme_location' => 'primary', 'walker' => new Acme_Mega_Walker(), 'container' => 'nav',
//                     'container_aria_label' => __( 'Primary', 'acme-theme' ) ) );

document.querySelectorAll('.acme-disclose').forEach((btn) => {
	const panel = btn.parentElement.querySelector(':scope > .acme-panel');
	const set = (open) => {
		btn.setAttribute('aria-expanded', String(open));
		panel.hidden = !open;
	};
	btn.addEventListener('click', () => set(panel.hidden));
	btn.parentElement.addEventListener('keydown', (e) => {
		if (e.key === 'Escape' && !panel.hidden) { set(false); btn.focus(); }
	});
});
document.addEventListener('click', (e) => {
	document.querySelectorAll('.acme-panel:not([hidden])').forEach((p) => {
		if (!p.parentElement.contains(e.target)) {
			p.hidden = true;
			p.parentElement.querySelector('.acme-disclose')?.setAttribute('aria-expanded', 'false');
		}
	});
});