JSFiddle - React, Tailwind, and code Playground

HTML

<iframe srcdoc="
<div id=a>
 From iframe
 <script>
  // This script will move the current parent <div> to the <iframe>'s parent
  // Since it's now in another document, the following script should not be executed nor downloaded
  // Still, it's going to be parsed and inserted into the parent DOM
  const div = document.getElementById('a');
  parent.document.body.append(div);
 </script>
 <script src='script.js'></script>
</div>"
></iframe>

JavaScript

onload = evt => console.log(document.querySelector("#a").outerHTML);