JSFiddle - React, Tailwind, and code Playground

HTML

<div id="wrap">
    <h1>Title</h1>
    <p>
        Some text and a <span>span</span>
    </p>
</div>

JavaScript

function walkTheDOM(node, func) {
    func(node);
    node = node.firstChild;
    while (node) {
        walkTheDOM(node, func);
        node = node.nextSibling;
    }
}

var root = document.getElementById('wrap');

walkTheDOM(root, function(node) {
    if ( node.nodeType === 1 ) { console.log( node.nodeName ); }
});