JSFiddle - React, Tailwind, and code Playground

HTML

<select>
  <option value="volvo">Volvo</option>
  <option value="saab">Saab</option>
  <option value="mercedes">Mercedes</option>
  <option value="audi">Audi</option>
</select>

JavaScript

var myIndex = document.querySelector('option[value="audi"]');
console.log(myIndex.index);