在Head之间添加下面的代码

<script type="text/javascript">
/*  动态网页标题*/
var OriginTitile = document.title,
titleTime;
document.addEventListener("visibilitychange",
function() {
    if (document.hidden) {
        $('[rel="shortcut icon"]').attr("href", "https://www.2x0.cn/favicon.ico");
        document.title = "你别走吖 Σ(っ °Д °;)っ";
        clearTimeout(titleTime)
    } else {
        $('[rel="shortcut icon"]').attr("href", "https://www.2x0.cn/favicon.ico");
        document.title = "你可算回来了 (｡•ˇ‸ˇ•｡)" + OriginTitile;
        titleTime = setTimeout(function() {
            document.title = OriginTitile
        },
        2000)
    }
});
</script>

利用visibilitychange的API
当浏览器标签页被隐藏或显示的时候会触发visibilitychange事件