Dynamic Focus/Blur Titles

(function () {
    // Title when tab has focus
    var fTitle = 'I promise, Jack!';
    // Title rotation list when tab is "blurred" (doesn't have focus)
    var bTitles = [
    'Come back!',
    '*blows whistle*'
    ];
    // Title rotation interval in milliseconds (e.g. 2000 = 2 seconds)
    var interval = 2000;
    var bti = 0, iv;

    function onFocus () {
    if (iv) {
        clearInterval(iv);
        iv = null;
    }
    document.title = fTitle;
    }

    function onBlur () {
    document.title = bTitles[bti++ % bTitles.length];
    if (bTitles.length > 1 && !iv) iv = setInterval(onBlur, interval);
    }

    document.title = fTitle;
    if (window.addEventListener) {
    addEventListener('focus', onFocus);
    addEventListener('blur', onBlur);
    } else if (window.attachEvent) {
    attachEvent('onfocus', onFocus);
    attachEvent('onblur', onBlur);
    }
})();