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

var $items = $('.testimonials .item');

function swap($a, $b){
    var $aNext = $a.next(),
        $aParent = $a.parent();
    $a.insertAfter($b);
    if($aNext.length) $b.insertBefore($aNext);
    else $aParent.append($b);
}

function shuffle($items){
    var i, j;
    for(i=$items.length-1; i>1; i--){
        j = Math.floor(Math.random() * (i+1));
        swap($items.eq(i), $items.eq(j));
    }
}

shuffle($items);

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

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