<!DOCTYPE html>
  <html lang='en'>
  <head>
    <meta charset='UTF-8'>
    <meta http-equiv='X-UA-Compatible' content='IE=edge'>
    <meta name='viewport' content='width=device-width, initial-scale=1.0'>
    <title></title>
  <style>
  * { box-sizing: border-box; }   
  main {
    background: #000;
  }
  .class {
    width: clamp(400px, 800px, 1200px);
  }
  </style>
  </head>
  <body>
    <div id="whatever">
      Lorem ipsum dolor sit amet consectetur adipisicing elit. Cupiditate 
      hic possimus libero veritatis officia. Voluptatum fuga non quibusdam 
      mollitia dolorum veritatis! Iure obcaecati facere quidem?
    </div>
  <script>
  const whatever = document.getElementById('whatever');  
  function doSomething() {
    blah baak; 
  }
  </script>
  </body>
  </html>