JSFiddle - React, Tailwind, and code Playground

HTML

<body>
    <ul>
      <li>test<sup title="this">hover</sup>
      <li>test<sup title="again"></sup>
      <li>test<sup title="more"></sup>
    <ul>
</body>

JavaScript

var supindexes = $("sup:empty");
$("sup:empty").text( function( index ) {
    return  index + 1 ;
});