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var __on = false;

var vis = (function(){
    var stateKey, eventKey, keys = {
        hidden: "visibilitychange",
        webkitHidden: "webkitvisibilitychange",
        mozHidden: "mozvisibilitychange",
        msHidden: "msvisibilitychange"
    };
    for (stateKey in keys) {
        if (stateKey in document) {
            eventKey = keys[stateKey];
            break;
        }
    }
    return function(c) {
        if (c) document.addEventListener(eventKey, c);
        return !document[stateKey];
    }
})();

var or = document.title;

vis(function () {
	if (!vis()) {
		__on = true;
		changeTitle();
	} else {
		__on = false;
		document.title = or;
	}
})

function changeTitle () {
	if (!__on) return;

	var a = '你有新消息';

	if (document.title == a) {
		document.title = or;
	} else {
		document.title = a;
	}

	setTimeout(changeTitle, 500);
}