<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8">
    <style>
    div {
      background-color: lime;
      height: 100px;
    }
    </style>
  </head>
  <body>
    <div class="short"></div>
    <script>
    "use strict";

    document.querySelector(".short").animate(
      { opacity: [1, 0] },
      {
        duration: 1,
        iterations: Infinity,
      }
    );
    </script>
  </body>
</html>
