JSFiddle - React, Tailwind, and code Playground

HTML

<html>
    <body>
        <div class="mark-first">My <strong>first</strong> word</div>
        <div>Nothing to see here!</div>
    </body>
</html>

CSS

div.mark-first span {
    color: red;
}

div.mark-first strong {
    font-weight: bold;
}

JavaScript

$('div.mark-first').each(function(){
     var me = $(this);
     me.html(me.html().replace(/^(\w+)/, '<span>$1</span>'));
});