初学drag，在使用dragstart时，源元素img的src属性值获取不到是怎么回事？src属性的值为undefined,麻烦各位大神看一下：
<!doctype HTML>
<html>
<head>
<meta charset="utf-8">
<title></title>
<meta name="description" content="">
<meta name="keywords" content="">
<style type="text/css">
html,body{
padding:0;
margin:0;
}
body{
font-family:\5b8b\4f53;
}
img{
border:0;
vertical-align:top;
}
.clear{
zoom:1;
}
.clear:after{
display:block;
clear:both;
content:"";
}
#example1{
width:1000px;
margin:0 auto;
background:#eee;
}
#source,#target{
width:180px;
height:126px;
background:#ddd;
}
#source{
float:left;
}
#target{
float:right;
text-align:center;
line-height:128px;
font-size:40px;
text-shadow:2px 2px 2px #666;
}
</style>
<script type="text/javascript">
window.onload=function(){
tool.drag();
}
var tool={};
tool.drag=function(){
var dragEle=document.getElementById("source");
var tar=document.getElementById("target");
dragEle.addEventListener("dragstart",start);
tar.addEventListener("dragover",move);
tar.addEventListener("drop",finish);
function start(){
var e=window.event || arguments[0];
var mySrc=dragEle.src;//获取不到src属性值，
var transfer=e.dataTransfer;
transfer.setData("img",mySrc);
};
function move(){
var e=window.event || arguments[0];
e.preventDefault();
};
function finish(){
var e=window.event || arguments[0];
var transfer=e.dataTransfer;
var myTarget=transfer.getData("img");
tar.innerHTML="<img src='"+myTarget+"' alt='' title='' width='180' />";
transfer.clearData("img");
}
}
</script>
</head>
<body>
<div id="example1" class="clear">
<div id="source"><img src="1.jpg" alt="" title="" width="180" /></div>
<div id="target">欢迎</div>
</div>
</body>
</html>
