W3Schools Tryit Editor

<!DOCTYPE HTML>
<html>
<style>
.droptarget {
  width: 100px; 
  height: 35px;
  padding: 10px;
  border: 1px solid black;
}
</style>

<body>
<h1>HTML DOM Events</h1>
<h2>The ondragstart Event</h2>

<p>Use the addEventListener() method to attach "dragstart", "dragend", "dragover" and "drop" events to the document object.</p>

<p>Drag the text up and down between the two rectangles:</p>

document.addEventListener("dragend", function(event) {
  document.getElementById("demo").innerHTML = "Finished dragging.";
});

/* Events fired on the drop target */
document.addEventListener("dragover", function(event) {
  event.preventDefault();
});

document.addEventListener("drop", function(event) {
  event.preventDefault();
  if ( event.target.className == "droptarget" ) {
    const data = event.dataTransfer.getData("Text");
    event.target.appendChild(document.getElementById(data));
  }
});
</script>

</body>
</html>