多点几次“open mywindow”按钮，“close mywindow”按钮就只能关闭最近的一个窗口，怎么回事儿？
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>多点几次“open mywindow”按钮，“close mywindow”按钮就只能关闭最近的一个窗口，怎么回事儿？</title>
</head>
<body>
<input type="button" value="Open myWindow" onclick="openWin()"/>
<input type="button" value="Close myWindow" onclick="closeWin()"/>
<script type="text/javascript">
function openWin(){
myWindow=window.open("","","width=400,height=200");
myWindow.document.write("This is myWindow");
}
function closeWin(){
myWindow.close();
}
</script>
</body>
</html>
