代码示例：（标识：jsref_window_closed）
<!DOCTYPE html>
<html>
<head>
<script>
var myWindow;
function openWin() {
myWindow = window.open("", "", "width=400 ,height=200");
}
function closeWin() {
if (myWindow) {
myWindow.close();
}
}
function checkWin() {
msg = ""
if (!myWindow) {
msg = "从未打开";
} else {
if (myWindow.closed) {
msg = "已关闭";
} else {
msg = "已打开";
}
}
document.getElementById("msg").innerHTML =
"myWindow " + msg;
}
</script>
</head>
<body>
<button onclick="openWin()">打开 myWindow</button>
<button onclick="closeWin()">关闭 myWindow</button>
<button onclick="checkWin()">myWindow 打开了吗？</button>
<br><br>
<div id="msg"></div>
</body>
</html>
