<!DOCTYPE html>
<html>
<head>
<title> new document </title>
<meta http-equiv="Content-Type" content="text/html; charset=gbk"/>
<script type="text/javascript">
function openWindow()
{
var open=confirm("新窗口打开网站");
if(open==true)
{
var url=prompt("请输入网址","http://www.imooc.com");
if(url!=null)
{
window.open(url,'_blank','witdh=400 height=500');
}
else
{
alert("null");
}
else
{
alert("null2")
}
}
}
</script>
</head>
<body>
<input type="button" value="新窗口打开网站" onclick="openWindow()" />
</body>
</html>
语法错误，if语句有if_else、if_else if_else两种，删除下面的即可运行
else {
alert("null2")
}
不熟悉