clock.html

<span></span>
<script>
const span = document.querySelector("span");
function step(timestamp) {
    const date = new Date();
    const d = {
       h: date.getHours().toString().padStart(2, '0'), 
       m: date.getMinutes().toString().padStart(2, '0'), 
       s: date.getSeconds().toString().padStart(2, '0'), 
       ms: Math.floor(date.getMilliseconds() / 100), 
    }
    span.textContent = `${d.h}:${d.m}:${d.s}.${d.ms}`;
    window.requestAnimationFrame(step);
}
window.requestAnimationFrame(step);
</script>