JSFiddle - React, Tailwind, and code Playground

HTML

<div id="foo">
  <ul>
    <li>foo
      <ul><li>bar</li></ul>
    </li>
    </ul>
</div>

<div>
 <ul><li>baz</li></ul>
</div>

JavaScript

console.log(d3.select('#foo').selectAll('div > ul').size())