JSFiddle - React, Tailwind, and code Playground

HTML

Hello Nurse

<p>Goodbye World</p>
<p>Cowboy says: Howdy</p>
<p>Why Hello there!</p>

CSS

span { background: #ddd }
.foo { background: #ff0 }

JavaScript

var regex = /(Hello|Goodbye)/g;

$('*').each(function() {
    var $this = $(this);
    var text = $this.text();
    if (regex.test(text)) {
        $this.html(
            $this.html().replace(regex, '<span>$1</span>')
        );
    }
});