JSFiddle - React, Tailwind, and code Playground

HTML

<div id="a">
  <div id="b"></div>
</div>

CSS

#a {
  padding: 50px;
  width: 100px;
  height: 100px;
  background-color: pink;
}
#b {
  width: 100px;
  height: 100px;
  background-color: green;
}

JavaScript

var div = document.querySelector('#a');
div.addEventListener('click', myFunc, false);
div.myParam = 'This is my parameter';
function myFunc(evt){
  window.alert(evt.target.myParam);
}