当用户切换了窗口后改变title，感觉挺有趣的，收藏了

(function() {
    var OriginTitile = document.title, titleTime;
    document.addEventListener('visibilitychange', function() {
        if (document.hidden) {
            document.title = '切换浏览器窗口';
            clearTimeout(titleTime);
        } else {
            document.title = '切回来';
            titleTime = setTimeout(function() {
                document.title = OriginTitile;
            },2000);
        }
    });
})();