JSFiddle - React, Tailwind, and code Playground

HTML

<div class="m1">1</div>
<div class="m1">2</div>
<div class="m1">3</div>
<div class="m1">4</div>
<div class="m1">5</div>

JavaScript

document.querySelectorAll(".m1")
  .forEach(i => i.onclick = e => { 
    e.target.style.backgroundColor = "red";
  });