JSFiddle - React, Tailwind, and code Playground

HTML

<div id="parent">
    <div id="child1">
        <div id="subchild1">
        </div>
    </div>
    <div id="child2">
        <div id="subchild2">
        </div>
    </div>
    <div id="child3">
        <div id="subchild3">
        </div>
    </div>
</div>

JavaScript

$(document).ready(function() {
      alert($('#parent [subchild]').length)
});