Node.firstChild & Node.lastChild

Get the first and last child nodes of a parent element, including nodes that aren’t elements (such as comments and text fragments).

<ul>
	<!-- The gray wizard -->
	<li>Gandalf</li>
	<li>Radagast</li>
	<li>Hermione</li>
	<!-- The surprise hero -->
	<li>Neville</li>
</ul>

let wizards = document.querySelector('ul');

// returns the comment node <!-- The gray wizard -->
let firstDescendant = wizards.firstChild;

// returns <li>Neville</li>
let lastDescendant = wizards.lastChild;