JSFiddle - React, Tailwind, and code Playground

HTML

<div class="parent"><span class="child">added to my parent</span></div>
<span class="single">added to me</span>
<br><br>
<a href="#" id="button">toggle</a>

CSS

.red-parent .child { background-color: red; }
.red-single { background-color: red; }

JavaScript

$(function() {
        $( "#button" ).toggle(
            function() {
                $( ".parent" ).addClass("red-parent",2000);
                //$( ".single" ).addClass("red-single",2000);
            },
            function() {
                $( ".parent" ).removeClass("red-parent",2000);
                //$( ".single" ).removeClass("red-single",2000);
            }
        );
    });