<?xml version="1.0" encoding="utf-8"?>
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
  <title>Image drag and drop: helper file</title>
  <script>
    function dropImage(event) {
      document.querySelector('div').firstChild.nodeValue = 'PASS';
    }
  </script>
</head>
<body>
  <div ondragenter="event.preventDefault()" ondragover="return false" ondrop="dropImage(event)">↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓
  </div>
</body>
</html>
