W3School TIY Editor

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

<p>本例使用 addEventListener() 方法将 "dragstart"、"dragenter"、"dragleave"、"dragover" 和 "drop" 事件附加到 document 对象。</p>

<p>在两个矩形之间来回拖动 p 元素：</p>

<p style="clear:both;"><b>注释：</b>Internet Explorer 8 及更早版本或 Safari 5.1 及更早版本不支持 drag 事件。</p>

/* 在放置目标上触发的事件 */
document.addEventListener("dragenter", function(event) {
  if ( event.target.className == "droptarget" ) {
    document.getElementById("demo").innerHTML = "Entered the dropzone";
    event.target.style.backgroundColor = "lightblue";
  }
});

document.addEventListener("dragover", function(event) {
  event.preventDefault();
});

/* 在放置目标上触发的事件 */
document.addEventListener("dragleave", function(event) {
  if ( event.target.className == "droptarget" ) {
    document.getElementById("demo").innerHTML = "Left the dropzone";
    event.target.style.backgroundColor = "";
  }
});

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

</body>
</html>