I recently also tried my hand at promises using the node libs Q and when. There's a gotcha with the progress handler. If you try to call the progress handler b

I recently also tried my hand at promises using the node libs Q and when. There's a gotcha with the progress handler. If you try to call the progress handler before the progress handler actually gets a chance to attach itself outside the function, it'll never actually fire. Some of the bugs with using promises are rather subtle.