Although callbacks are the standard way of dealing with asynchronous methods in JavaScript they can get out of hand easily. There are a number of approaches to solving this spaghetti code: promise libraries provide a more fluent way of handling callbacks and future versions of JavaScript may adopt an approach similar to the C# async/await syntax.

I really like accumulators but they can be inefficient in terms of memory use. The lack of tail recursion means that each pass through adds another stack frame, so this approach may result in memory pressure. All things are a trade-off in this case between memory and code maintainability.