JSFiddle - React, Tailwind, and code Playground

HTML

<ul>
    <li>An item</li>
</ul>
<button id="foo">Click me</button>
<button id="bar">Me too</button>

JavaScript

$(function() {
    var old = {
        appendChild: Element.prototype.appendChild
    };

    var selector = "ul li.foo";

    Element.prototype.appendChild = function(node) {
        var retval = old.appendChild.apply(this, arguments);
        if ($(node).is(selector)) {
            alert("Matching element inserted!");
        }
        return retval;
    };
    
    $("button").on('click', function() {
        $("ul").append("<li class=" + this.id + ">A dynamically added item</li>");
    });
});