JSFiddle - React, Tailwind, and code Playground

HTML

<div id="loco" class="hey" >lorem ipsum pendus <em>hey</em>moder <hr /></div>

CSS

em { font-style: italic; }

JavaScript

(function iterate_node(node) {
    if (node.nodeType === 3) { // Node.TEXT_NODE
        var text = node.data,
            words = text.split(/\s/);
        if (words.length > 1) {
            node.data = words[0];
            var next = node.nextSibling,
                parent = node.parentNode;
            for (var i=1; i<words.length; i++) {
                var tnode = document.createTextNode(words[i]),
                    br = document.createElement("br");
                parent.insertBefore(br, next);
                parent.insertBefore(tnode, next);
            }
        }
    } else if (node.nodeType === 1) { // Node.ELEMENT_NODE
        for (var i=node.childNodes.length-1; i>=0; i--) {
            iterate_node(node.childNodes[i]); // run recursive on DOM
        }
    }
})(document.getElementById("loco")); // any dom node