jQuery: Promise and Deferred with getJSON

promise.js

//http://nurkiewicz.blogspot.com/2013/03/promises-and-deferred-objects-in-jquery.html
function doubleAjax() {
    var deferred = $.Deferred();
    $.getJSON('square/3', function(threeSquare) {
        deferred.notify(threeSquare)
        $.getJSON('square/4', function(fiveSquare) {
            deferred.resolve(fiveSquare);
        });
    });
    return deferred.promise();
}
 
doubleAjax().
progress(function(threeSquare) {
    console.info("In the middle", threeSquare);
}).
done(function(fiveSquare) {
    console.info("Done", fiveSquare);
});