Effect clock

Use $effect for side effects and cleanup.

<script>
  let now = $state(new Date());
  $effect(() => {
    const id = setInterval(() => { now = new Date(); }, 1000);
    return () => clearInterval(id);
  });
</script>

<p>{now.toLocaleTimeString()}</p>

<style>p{font:700 1.5rem/1 ui-monospace,monospace;color:#18181b}</style>