<?xml version="1.0" encoding="utf-8"?>
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>Selection drag and drop: changing dropzone attribute ondragstart</title>
<style type="text/css">
div
	{display:inline-block;
	vertical-align:top;
	background-color:olive;
	color:white;
	padding:20px;
	width:100px;
	height:100px;}
div:nth-child(2)
	{background-color:green;}
div:nth-child(3)
	{background-color:teal;}
</style>
<script type="application/ecmascript">
var effects = ['copy','move','link'];
function selectText()
	{window.getSelection().selectAllChildren(document.querySelector('p'))}
function dropSelection(event,element)
	{document.querySelectorAll('div')[element].appendChild(document.createTextNode((event.dataTransfer.dropEffect == effects[element])?' PASS ':' FAIL '));
	selectText();}
function start(event)
	{for(var i = 0; i != 3; i++)
		{document.querySelectorAll('div')[i].setAttribute('dropzone',effects[i] + ' string:text/plain')}
	}
</script>
</head>
<body onload="selectText()">
<div ondrop="dropSelection(event,0)" dropzone="link string:text/plain"/>
<div ondrop="dropSelection(event,1)" dropzone="copy string:text/plain"/>
<div ondrop="dropSelection(event,2)" dropzone="move string:text/plain"/>
<p ondragstart="start(event)">Drag me</p>
<p>You should be able to drag selection and drop it onto any of the green boxes.</p>
</body>
</html>