各位帮忙看下，怎么都是出现undefined？自己打了好几遍 找不到原因
<!DOCTYPE HTML>
<html >
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>数组</title>
<script type="text/javascript">
var a=['*','##','***',"&&","****","##*"];
a[7]="**";
alert(a.length);
for(var i=0;i<a.length;i++){
a[i]=new Array();
document.write(a["+i+"]+"</br>");
}
</script>
</head>
<body>
</body>
</html>
