在元素正在拖动到放置目标时触发 - 在线编辑器

          <!DOCTYPE HTML>
<html>
<head>
  <meta charset="utf-8">
  <title>蜜蜂教程(mifengjc.com)</title>
  <style>
    #droptarget {
      float: left;
      width: 200px;
      height: 35px;
      margin: 55px;
      margin-top: 155px;
      padding: 10px;
      border: 1px solid #aaaaaa;
    }
  </style>
</head>
<body>

  <p ondragstart="dragStart(event)" draggable="true" id="dragtarget">把我拖动到矩形框中！</p>
  <div id="droptarget" ondrop="drop(event)" ondragover="allowDrop(event)">
  </div>
  <p style="clear:both;"><strong>注意：</strong>Internet Explorer 8 及更早 IE 版本或 Safari 5.1 及更早版本的浏览器不支持 drag 事件。</p>
  <p id="demo"></p>
  <script>
    function dragStart(event) {
      event.dataTransfer.setData("Text", event.target.id);
    }

    function allowDrop(event) {
      event.preventDefault();
      document.getElementById("demo").innerHTML = " p 元素在放置目标上";
      event.target.style.border = "4px dotted green";
    }

    function drop(event) {
      event.preventDefault();
      var data = event.dataTransfer.getData("Text");
      event.target.appendChild(document.getElementById(data));
      document.getElementById("demo").innerHTML = " p 元素被拖动";
    }
  </script>

</body>
</html>
        