The Element.firstElementChild read-only property returns an element's first child Element, or null if there are no child elements.
Element.firstElementChild includes only element nodes. To get all child nodes, including non-element nodes like text and comment nodes, use Node.firstChild.
An Element object, or null.
<ul id="list">
<li>First (1)</li>
<li>Second (2)</li>
<li>Third (3)</li>
</ul>const list = document.getElementById("list");
console.log(list.firstElementChild.textContent);
// logs "First (1)"