JSFiddle - React, Tailwind, and code Playground

HTML

<span>foo</span>
<pre id="result"></pre>

CSS

span:before { content: '['; }
span:after { content: ']'; }

JavaScript

var res = document.getElementById('result');
var span = document.getElementsByTagName('span')[0];
res.innerText += 'span has ' + span.childNodes.length + ' child: ' + span.childNodes[0].data;