Alternative functional approach to dealing with the async pyramid. This is a response to http://wekeroad.com/2012/04/05/cleaning-up-deep-callback-nesting-with-nodes-eventemitter/

registerCustomer.coffee

validate = (customer, next)->
  console.log 'validating...'
  #VALIDATE HERE
  next()

insert = (customer, next)->
  console.log 'inserting...'
  # insert into DB (asynchronously of course), and then call...
  next()

sendEmail = (customer, next)->
  console.log 'sending email...'
  # send email (asynchronously of course), and then call...
  next()
  

registerCustomer = ( customer, successCallback )->
  # WORKFLOW
  afterValidate = (customer,next)-> insert( customer, afterInsert )
  afterInsert = (customer,next)-> sendEmail( customer, afterEmail )
  afterEmail = (customer,next)-> successCallback( customer )

  validate( customer, afterValidate )

module.exports = registerCustomer

registerCustomer.js

// A compiled version of the coffeescript, for those that don't like coffeescript


var insert, registerCustomer, sendEmail, validate;

validate = function(customer, next) {
  console.log('validating...');
  return next();
};

insert = function(customer, next) {
  console.log('inserting...');
  return next();
};

sendEmail = function(customer, next) {
  console.log('sending email...');
  return next();
};

registerCustomer = function(customer, successCallback) {
  var afterEmail, afterInsert, afterValidate;

  // WORKFLOW DEFINED HERE

  afterValidate = function(customer, next) { return insert(customer, afterInsert); };
  afterInsert = function(customer, next) { return sendEmail(customer, afterEmail); };
  afterEmail = function(customer, next) { return successCallback(customer); };


  // START WORKFLOW
  return validate(customer, afterValidate);
};

module.exports = registerCustomer;

sample_usage.js

var registerCustomer = require('registerCustomer');

console.log('registering customer...');
registerCustomer('dummy customer data', function() {
  return console.log('customer registered!');
});

Got here after googling Rob Conery's article. In lines 19-21, the (customer,next) parameters on the functions being defined are superfluous, no? The after_ functions are being called with next(), having no params passed in...