为什么点击不会出现框
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>请与我互动</title>
<script>
function openWindow(){
var judge=confirm('要新窗口打开网址吗?');
var shufu;
if(judge==true)
{
shufu=prompt("请输入网址","http://www.imooc.com/");
window.open(shufu.'_blank','height=400,width=500,menubar=no,toolbar=no');
}
}
</script>
</head>
<body>
<input type="button" value="新窗口打开网站" onclick="openWindow()" />
</body>
</html>