JSFiddle - React, Tailwind, and code Playground

HTML

<div id="master_element">
  <a href="#" id="link">Erp. a text</a>

  **This must be the only text replaced**

  <em>Herp. em text</em>
  <div id="nest_meh">
    <div id="we_need_to_dig_deeper">
      nested div from hell
    </div>
  </div>
</div>

JavaScript

document.getElementById('link').nextSibling.nodeValue = 'something else';