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                <p>Hover over each box for 1s. Once the border has finished changing color, the background-color should be changed to red.</p>

<p>Using <code>transition: none;</code> prevents <code>transitionend</code> event from being fired.</p>

<div class="box">Border changes for 1s, then background changes after anim </div>
<div class="box no-anim">Border instant, background never changes</div>
<div class="box short-anim">Border instant, background instant</div>


                .box {
  border: solid 6px;
  transition: border-color 1s;
  width: 100px;
  height: 100px;
  margin: 20px;
  padding: 8px;

.box:hover {
  border-color: blue;

.no-anim {
  transition: none;

.short-anim {
  transition-duration: 0.01s;


                let boxes = document.querySelectorAll('.box')

boxes.forEach(box => {
  box.ontransitionend = () => { = 'background-color: red'