I've happily used the async module for Node.js for years to simplify asynchronous operations over arrays. This is a difficulty in the Node.js paradigm, since the "normal" way to process an array is with a simple for loop. But if the operation is asynchronous the for loop has no way of knowing when to iterate to the next item, or even when processing is finished. Instead the async.eachSeries function does the trick, because your code tells async.eachSeries when to go to the next item, when there's an error, and it knows when the last item is processed, etc. It's been great.