JSFiddle - React, Tailwind, and code Playground

HTML

<select multiple id="mySelect">
  <option>Apple</option>
  <option>Orange</option>
  <option>Pineapple</option>
  <option>Banana</option>
</select>

JavaScript

document.getElementById("mySelect").onclick = function() {
 	alert(this.selectedIndex);
 };