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, i;
list = document.getElementsByClassName("even, odd");
for (i = 0; i < list.length; ++i) {
    list[index].setAttribute('class', 'cf');
}