<!DOCTYPE html>
<style>
#wrapper::first-line {}
</style>
<body>
<div id="wrapper">
  <div id="test"></div>
</div>
<script>
  document.querySelector('#test').style.position = 'absolute';
  document.body.offsetHeight;
  document.querySelector('#wrapper').style.color = 'green';
  document.querySelector('#test').style.position = '';
</script>
</body>