Arrow function javascript

<!DOCTYPE html>
<html>

<head>
  <title>Arrow function javascript</title>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width">
  <style>

    .clone {
      position: absolute;
      top: 10px;
      left: 10px;
      text-decoration: none;
      background-color: snow;
      width: 150px;
      text-align: center;
      color: red;
      font-family: arial black;
      padding: 5px 20px;
    }

    body {
      background-color: red;
    }

    h1 {
      font-size: 40px;
      font-family: courier;
      text-indent: 100px;
      text-align: justify;
      padding: 0 20px;
      color: snow;
      font-style: italic;
    }
  </style>
</head>

<body>
  <h1 id='p'></h1>

  <a class='clone' title="Subscribe and hit the notification bell for more updates. It's free." href='https://www.youtube.com/channel/UCqLpDK0eOsG1eEeF9jOUZkw'>SUBSCRIBE</a>


  <script>
    post = 'One morning, when Gregor Samsa woke from troubled dreams, he found himself transformed in his bed into a horrible vermin. He lay on his armour-like back, and if he lifted his head a little he could see his brown belly, slightly domed and divided by arches into stiff sections. ';
    i = 0;
    setTimeout(function() {
      (start = () => {
        x = requestAnimationFrame(start);
        p.innerHTML += post[i];
        i++;
        if (i == post.length) {
          cancelAnimationFrame(x);
        }
      })();
    }, 2000);
  </script>
</body>
</htm>