Page Visibility + speech

needy.js

var tabAway;
tabAway = {
    init: function () {
        var _this = tabAway;
        _this.bindEvents();
    },
    data: {
        tabAwayMsg: "Don't go, I need you!",
        tabBackMsg: "I knew you'd never leave me",
    },
    helpers: {
        hiddenProp: function () {
            var prefixes = ['webkit','moz','ms','o'];
            if ('hidden' in document) return 'hidden';
            for (var i = 0; i < prefixes.length; i++){
                if ((prefixes[i] + 'Hidden') in document){ 
                    return prefixes[i] + 'Hidden';
                }
            }
            return null;            
        },
        isHidden: function () {
            var _this = tabAway,
                prop = _this.helpers.hiddenProp();
            if (!prop) return false;
            
            return document[prop];
        },
        createSpeech: function (msg) {
            return new SpeechSynthesisUtterance(msg);
        }
    },
    bindEvents: function () {
        var _this = tabAway,
            visProp = _this.helpers.hiddenProp();
        if (visProp) {
          var evtname = visProp.replace(/[H|h]idden/,'') + 'visibilitychange';
          document.addEventListener(evtname, _this.functions.handleVischange);
        }
    },
    functions :{
        handleVischange: function () {
            var _this = tabAway,
                hidden = _this.helpers.isHidden(),
                msg = hidden === true ? _this.data.tabAwayMsg : _this.data.tabBackMsg,
                spokenMsg = _this.helpers.createSpeech(msg);
                console.log(msg);
            _this.functions.speakMessage(spokenMsg);
        },
        speakMessage: function (msg) {
            window.speechSynthesis.speak(msg); 
        }
    }
}
tabAway.init();