W3Schools Tryit Editor

<!DOCTYPE html>
<html>
<title>W3.CSS</title>
<meta name="viewport" content="width=device-width, initial-scale=1">
<link rel="stylesheet" href="https:/edu/w3css/5/w3.css">
<body class="w3-container">

<h2>Fading Slides</h2>
<p>The <b>w3-animate-fading</b> class animates an element in and out (takes about 10 seconds).</p>

function carousel() {
  const slides = document.querySelectorAll(".mySlides");

slides.forEach(slide => {
    slide.style.display = "none";
  });

slideIndex++;

if (slideIndex > slides.length) {
    slideIndex = 1;
  }

slides[slideIndex - 1].style.display = "block";

setTimeout(carousel, 9000);
}
</script>

</body>
</html>