JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://unpkg.com/umbrellajs"></script>
<a>A</a>
<a>B</a>
<a>C</a>
<a>D</a>

CSS

.odd {
  background: #faa;
}

JavaScript

u('a').addClass((el, i) => (i % 2 == 0) ? 'odd' : '');