<!DOCTYPE html>
<html lang="ja-JP">
<head>
<title>Pop Up</title>
<meta charset="UTF-8" />
<script>
var notifyClose = function() {
window.opener.document.getElementById('closed-flg').checked = true;
};
window.onbeforeunload = notifyClose;
</script>
</head>
<body onunload="notifyClose();" >
Popup Page
</body>
</html>