JSFiddle - React, Tailwind, and code Playground

HTML

<a href="#" class="Titanic">1</a>
<a href="#" class="">2</a>
<a href="#" class="">3</a>
<a href="#" class="Titanic">4</a>

JavaScript

var el = [];
for (var i = 0; i < document.links.length; i++) {
    if (document.links[i].className == 'Titanic') {
        el.push(document.links[i]);
    }
}

for (var i = 0; i < el.length; i++) {
    el[i].style.backgroundColor = 'yellow';
}