    <!DOCTYPE html>
    <html>
    <head>
      <meta charset="UTF-8">
      <title>자동 스크롤하기</title>
      <link rel="stylesheet" href="style_js.css">
    </head>
    <body style="text-align: center">
      <h2>자동 스크롤</h2><hr>
      <script>
        for (let i = 1; i <= 25; i++)
          document.write(i + '<hr>');

        let pos = 0;
        const speed = 40;      // 위아래 스크롤 속도
        setInterval(function() {
          window.scrollBy(0, speed);
          pos = pos + speed;
          if (pos >= innerHeight + speed) {
            pos = 0;
            window.scrollTo(0, 0);
          }
        }, 500);
      </script>
    </body>
    </html>