JSFiddle - React, Tailwind, and code Playground

HTML

<div></div>
<p>There should be no alert saying 'transitionend'</p>

CSS

div {
    background-color: lightblue;
    width: 100px;
    height: 100px;
    left: 0px;
    position: absolute;
}

JavaScript

var div = document.querySelector('div');
div.addEventListener('transitionend', () => alert('transitionend'));
div.style.transition = 'left 3s';
div.style.left = '100px';
setTimeout(function() {
    div.style.transitionDuration = '1s';
    div.style.transitionDelay = '-1s';
    div.style.left = '300px';
}, 1500);