JSFiddle - React, Tailwind, and code Playground

HTML

<a class='nulll'><div class="three">THREE</div></a>
<a class="two"><div class="one">one</div></a>

JavaScript

(function() {
    document.getElementsByClassName('one')[0].onmouseover = function() {
        document.getElementsByClassName('three')[0].style.color = 'red';
    }
})();