Node.js: What techniques are there for writing clean, simple callback code?

Question

node.js code is known for turning into callback spaghetti.

What are the best techniques for overcoming this problem and writing clean, uncomplex, easy to understand

Answer 1

I'd suggest 1) using CoffeeScript and 2) using named callbacks and passing state between them in a hash, rather than either nesting callbacks or allowing argument lists to get very long. So instead of

var callback1 = function(foo) {
  var callback2 = function(bar) {
    var callback3 = function(baz) {
      doLastThing(foo, bar, baz);
    }
    doSomethingElse(bar, callback3);
  }
  doSomething(foo, callback2);
}
someAsync(callback1);

you can instead simply write

callback1 = (state) -> doSomething state.foo, callback2
callback2 = (state) -> doSomethingElse state.bar, callback3
callback3 = (state) -> doLastThing state
someAsync callback1

once your doSomething, doSomethingElse and doLastThing have been rewritten to use/extend a hash. (You may need to write extra wrappers around external functions.)

As you can see, the code in this approach reads neatly and linearly. And because all callbacks are exposed, unit testing becomes much easier.