JSFiddle - React, Tailwind, and code Playground

HTML

<div class="sliderhighlight">
</div>
<div class="sliderhighlight">
</div>
<div class="sliderhighlight">
</div>

CSS

.sliderhighlight {
  width: 100px;
  height: 100px;
  background: red;
  margin-bottom: 2px;
}

JavaScript

var sliderHighlight = document.getElementsByClassName("sliderhighlight");

function clickPointer() {
  alert("Hello");
  this.style.background = "blue";
}
for (var i = 0; i < sliderHighlight.length; i++) {
  sliderHighlight[i].addEventListener("click", clickPointer);
}