JSFiddle - React, Tailwind, and code Playground

HTML

<div class="itemRelated">
    <ul>
        <li class="even">Hi There</li>
        <li class="odd">Whats'up</li>
        <li class="even">BugsBunny</li>

CSS

.cf {
    color:red;
}

JavaScript

var list = document.querySelectorAll(".even, .odd");
for (var i = list.length; i--;) {
    list[i].className = list[i].className + ' cf';
}