css/css-conditional/container-queries/counters-in-container-dynamic.html

<!doctype html>
<title>CSS Container Queries Test: counter updates</title>
<link rel="help" href="https://drafts.csswg.org/css-conditional-5/#container-type">
<link rel="match" href="counters-ref.html">
<style>
  #container {
    container-type: size;
    width: 200px;
    height: 200px;
  }

  #counter::before {
    content: counter(my-counter);
  }

  @container (min-width: 300px) {
    #counter {
      counter-reset: my-counter 100;
    }
  }
</style>
<p>Pass if you see the number 100 below.</p>
<div id="container">
  <div id="counter"></div>
</div>
<script>
  container.offsetTop;
  container.style.width = "400px";
</script>