JSFiddle - React, Tailwind, and code Playground

HTML

<input type="hidden" value='
Hahaha <fake tag="something"> Bliep
   <div>&amp; ampersand entity fail..<br>
      <input type="" value="" />
   </div> 
'/><textarea></textarea>
<hr>Control:
<textarea>
Hahaha <fake tag="something"> Bliep
   <div>&amp; ampersand entity fail..<br>
      <input type="" value="" />
   </div> 
</textarea>

CSS

textarea{width:99%;height:250px;}

JavaScript

document.getElementsByTagName('textarea')[0].value=document.getElementsByTagName('input')[0].value;