【原创】javascript 关闭窗口前提示

    <script src="scripts/jquery-1.4.1.js" type="text/javascript"></script>
    <script type="text/javascript">
        $(
        function () {
            $.post("Handler.ashx", {}, function (data) {
                datafrom = data;
            });
        }
        );


        window.onbeforeunload = beforeUnload;
        window.onunload = unload;

        var datafrom = "";
        var gotobaidu = false;
        function beforeUnload() {

            if (confirm(datafrom)) {
            }
            else {
                window.location.href = "http://www.baidu.com";
            }
        }
        function unload() {

        }
    </script>