JSFiddle - React, Tailwind, and code Playground

HTML

<div class="newDiv">
  Test
</div>
<div class="newDiv">
  Another test
</div>
<div class="newDiv">
  One last test
</div>

CSS

.newDiv {
  background-color: red;
}

JavaScript

let tiles  = document.getElementsByClassName('newDiv');

for (let i = 0; i < tiles.length; i++) {
	tiles[i].addEventListener('mouseover', function(e){
  	tiles[i].style.backgroundColor = "black"});
}