JSFiddle - React, Tailwind, and code Playground

HTML

<script src="//ajax.googleapis.com/ajax/libs/jquery/1.10.2/jquery.min.js"></script>
<div><span class="admin-stats-big-figures">One</span> &nbsp; </div>
<div><span class="admin-stats-big-figures-hidden">Two</span> &nbsp; </div>
<hr/>
<input type="button" value="Start" onclick="myAnim.start()"/> | <input type="button" value="Stop" onclick="myAnim.stop()"/>

JavaScript

var myAnim = {
                elements : null,
                interval : null,
                delay : { fade: 500, anim: 200 },
                init : function(classNameOne, classNameTwo, fadeDelay, animDelay) {
                    this.elements = [$("."+classNameOne),$("."+classNameTwo)];
                    if (animDelay) this.delay.anim = animDelay;
                    if (fadeDelay) this.delay.fade= fadeDelay;
                    this.elements[0].fadeOut(function(){myAnim.start()});
                },
                update : function() {
                    this.elements[0].fadeToggle(this.delay.anim,function(el,delay){el.fadeToggle(delay)}(this.elements[1],this.delay.anim));
                },
                start : function() {
                    if (this.interval) return;
                    this.interval = setInterval(function(){myAnim.update()},this.delay.fade);
                },
                stop : function () {
                    if (!this.interval) return;
                    clearInterval(this.interval);
                    this.interval = null;
                }
            }

            $(document).ready(
              function(){
                  myAnim.init("admin-stats-big-figures","admin-stats-big-figures-hidden",500,200);
              }
            );