The third slide is out of date. 1.30 removed support for promises. All previously promised-based functions now take a callback parameter as their last argument instead, so the slide would be written:

    posix.rename("/tmp/hello", "/tmp/world",
        function() {
            posix.unlink("/tmp/world");
        });

There are a series of articles on howtonode.org about flow control in node and cleaner ways to do this. Not mentioned on howtonode, but Kris Zyp also implemented a CommonJS promises library on the node callback pattern.