Native Javascript Loading effect

<!doctype html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <style>
      body {
        height: 200;
        overflow: hidden;
        background-color: #696969;
        font-family: 'Roboto', 'Courier New', monospace;
      }

      .flex {
        display: flex;
        justify-content: center;
        align-items: center;
        height: 150px;
      }

      img {
        height: 100px;
      }

      .center {
        text-align: center;
      }

      .white {
        color: white;
      }

      .bold {
        font-weight: bold;
      }

      p {
        min-width: 110px;
      }

      #loading {
        text-align: right;
        width: 75px;
        display: inline-block;
      }

      #loadingValue {
        text-align: left;
        width: 35px;
        display: inline-block;
      }
    </style>

    <script>
      function main() {
        const el = document.getElementById('loadingValue');
        el.innerHTML = '.';
        setInterval(() => {
          if (el.innerHTML.length + 1 <= 3) el.innerHTML += '.';
          else el.innerHTML = '';
        }, 1000);
      }
    </script>
  </head>
  <body onload="main()">
    <div class="flex">
      <img src="/icon.png" alt="Logo" height="150" />
    </div>
    <div>
      <p class="center">
        <span class="white bold" id="loading">Loading</span>
        <span id="loadingValue"></span>
      </p>
    </div>
  </body>
</html>

I ain't a frontend developer, like at all. so if the CSS is disgusting... Sorry :/

This html code generates something like this

It loops 3 times and resets the string every 3 iterations.
It waits 1 second to print the next character