[UX] window.onbeforeunload 页面卸载事件

防止用户误操作离开页面

Open <a href="http://www.baidu.com">baidu</a>.
<script>
window.onbeforeunload = function (e) {
    var e = e || window.event;
    // For IE and Firefox prior to version 4
    if (e) {
        e.returnValue = 'Any string';
    }
    // For Safari
    return 'Any string';
};
</script>