再帰 with promise pattern ref: http://qiita.com/items/86ad078cd6d9e1bf0a3d

file0.txt

function fact(n) {
  var d = $.Deferred();
  setTimeout(function() {
    function onResolved(result) {
      d.resolve(result * n);
    }
    n > 1 ? fact(n - 1).then(onResolved) : d.resolve(n);
  }, 100);
  return d.promise();
}

fact(5).then(console.log.bind(console)); // 120