JSFiddle - React, Tailwind, and code Playground

HTML

<div id="mainContainer">
  <h1>Heading</h1>
  <p>Paragraph.</p>
</div>

JavaScript

function mutate(mutations) {
  mutations.forEach(function(mutation) {
    alert(mutation.type);
  });
}

jQuery(document).ready(function() {
  setTimeout(function() {
    document.querySelector('div#mainContainer > p').textContent = 'Some other text.';
  }, 2000);
  
  var target = document.querySelector('div#mainContainer > p')
  var observer = new MutationObserver( mutate );
  var config = { characterData: true, attributes: false, childList: false, subtree: true };

  observer.observe(target, config);
});