JSFiddle - React, Tailwind, and code Playground
HTML
<p id = "text">
Lorem ipsum dolor sit amet.
</p>
<p id = "result"># of vowels: <span></span></p>
JavaScript
$(function() {
var vowelsCount = $("#text").text().match(/[aeiou]/gi).length;
$("#result > span").html(vowelsCount);
});