(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);        }    });})();