如何使div在提交时随过渡消失？

.fade-out {
  opacity: 0;
  transition: opacity 0.5s ease-out;
}

<div id="myDiv" class="fade-out">
  <!-- div内容 -->
  <button type="submit" onclick="submitForm()">提交</button>
</div>

function submitForm() {
  var div = document.getElementById("myDiv");
  div.classList.remove("fade-out");
}