window onBlur onFocus

JavaScript

var x = null;

function flashMe () {
    var szTitle = document.title;
    
    if (szTitle.substring(0,1) == '.') {
        document.title = 'This is a actual title';
    } else {
        document.title = '. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ';
    }
}

function onBlur() {
    x = setInterval(flashMe, 500);
    console.log('onBlur')
};
function onFocus(){
    if (x) clearInterval(x);
    x = null;
    console.log('onFocus')
};

if (/*@cc_on!@*/false) { // check for Internet Explorer
    document.onfocusin = onFocus;
    document.onfocusout = onBlur;
} else {
    window.onfocus = onFocus;
    window.onblur = onBlur;
}