NAV

<script>
	const button = document.querySelector('button[popovertarget=demo-mobile-nav-waapi]');
	const close_button = document.querySelector('.close');
	const popover = document.querySelector('#demo-mobile-nav-waapi');

	button.addEventListener('click', toggle);
	close_button.addEventListener('click', toggle);

	function toggle(e) {
		e.preventDefault();

		const is_opening = !popover.matches(':popover-open');
		const translate = is_opening ? ['100vi', '0'] : ['0', '100vi'];

		if (is_opening) popover.showPopover();

		window.requestAnimationFrame(() => {
			let animation = popover.animate(
				{
					translate,
				},
				{
					duration: 300,
					easing: 'ease-in-out',
					fill: 'forwards',
				},
			);
			animation.onfinish = () => {
				if (!is_opening) popover.hidePopover();
			};
		});
	}

	document.addEventListener('keydown', (e) => {
		if (e.key === 'Escape' && popover.hasAttribute('popover') && popover.matches(':popover-open')) {
			toggle(e);
		}
	});
</script>

<button popovertarget="demo-mobile-nav-waapi">NAV</button>

<nav popover id="demo-mobile-nav-waapi">
	<button class="demo-button close">Close Nav</button>
	<ul>
		<li><a href="#">Home</a></li>
		<li><a href="#">About</a></li>
		<li><a href="#">Store</a></li>
		<li><a href="#">Contact</a></li>
	</ul>
</nav>

<style>
	#demo-mobile-nav-waapi[popover] {
		margin: 0;
		block-size: 100vb;
		inline-size: 90vi;
		inset-inline-start: unset;
		inset-inline-end: 0;
	}
</style>