JSFiddle - React, Tailwind, and code Playground

HTML

<ul>
    <li  data-details="li1">first</li>
    <li  >second</li>
</ul>

JavaScript

$(document).ready(function()
                  {
                      $("ul li:nth-child(2)").data("details","li2");
                      console.log($("ul li:nth-child(2)").data());
                      alert($("ul li[data-details='li1']").length);
                      alert($("ul li[data-details='li2']").length);
                  });