web-animations-api/implicit-keyframes.html

<!doctype html>
<html lang="en-US">

<head>
  <meta charset="utf-8">
  <title>Web Animations API implicit keyframes</title>
  <style>
    html {
      height: 100%;
    }

    body {
      margin: 0;
      height: inherit;
      display: flex;
      justify-content: center;
      align-items: center;
    }

    div {
      width: 150px;
      height: 100px;
      background-color: red;
      border: 10px solid black;
      border-radius: 10px;
    }
  </style>
</head>

<body>
  <div>

  </div>

  <script>
    const divElem = document.querySelector('div');

    let rotate360 = [
      { transform: 'rotate(360deg)' }
    ];

    let slowInfinite = {
      duration: 5000,
      iterations: Infinity
    }

    divElem.animate( rotate360, slowInfinite );

  </script>
</body>

</html>