JSFiddle - React, Tailwind, and code Playground

HTML

<div class="testowyDiv">
    <img class="carousel-button-left" src="ikony/strzalkal.png">
    <div class="testowyDiv2">
        <ul class="testowyUl">
            <li>1</li>
            <li>2</li>
            <li>3</li>
            <li>4</li>
            <li>5</li>
            <li>6</li>
            <li>7</li>
            <li>8</li>
            <li>9</li>
        </ul>
    </div>
    <img class="carousel-button-right" src="ikony/strzalkap.png">
</div>

JavaScript

$(document).ready(function(){   
    $(".carousel-button-left").click(function(){
    var $ul=$(".testowyUl");   
    var lastchild=$ul.children().last();
        console.log(lastchild.val());
    $ul.prepend(lastchild);
    });
});