JSFiddle - React, Tailwind, and code Playground

HTML

<div class="testimonials">
<div class="item">item 1</div>
<div class="item">item 2</div>
<div class="item">item 3</div>
<div class="item">item 4</div>
</div>

CSS

.item {display:none;}

JavaScript

$('.testimonials div:first').show();

setInterval(function(){ $('.testimonials div:first-child').fadeOut(1000).next('div').delay(1000).fadeIn(1000).end().appendTo('.testimonials') },3000);