JSFiddle - React, Tailwind, and code Playground

HTML

<div class="block test"></div>
<div class="menu block"></div>
<div class="block test2"></div>

CSS

body {
  display: flex;
 justify-content: space-between;
}
.block {
  width: 200px;
  height: 200px;
  background: blue;
  display: inline-block;
  margin: 10px;
  color:#fff;
}

JavaScript

document.addEventListener('mousemove', event => {
  if (!event.target.classList.contains('menu')) {
    if (event.target.classList.contains('block')) {
      event.target.textContent = event.target.className
    }

  }
  console.log(event.target.className)
}, false);