W3Schools Tryit Editor

<!DOCTYPE HTML>
<html>
<head>
<style>
.droptarget {
  float: left; 
  width: 100px; 
  height: 35px;
  margin: 15px;
  padding: 10px;
  border: 1px solid #aaaaaa;
}
</style>
</head>
<body>

<p>Drag the p element back and forth between the two rectangles:</p>

function dragEnd(event) {
  document.getElementById("demo").innerHTML = "Finished dragging the p element.";
}

function allowDrop(event) {
  event.preventDefault();
}

function drop(event) {
  event.preventDefault();
  let data = event.dataTransfer.getData("Text");
  event.target.appendChild(document.getElementById(data));
}
</script>

</body>
</html>