Pseudo AsyncNess

async.example.js

//  npm install async
//  installs to ./node_modules

var db;  // Pretend this is a valid async DB connection

var async = require('async');

var bigArray      = [];  // Pretend this is full of data
var returnResults = [];  // Pretend this is empty

// Secondary async function
var doStuff(item, cb) {
  db.findOne({ item.id }, function(err, doc) {
    // We have docs related to item.id
    returnResults.push(doc);
    cb();
  });
};

// Primary async item function, called by async.forEach below
var doFunction = function(item, callback) {

  doStuff(item, callback);
};

// Now that we've defined helper functions, lets actually do something
async.forEach(bigArray, doFunction, function() {

  console.log(returnResults);  // Will return results AFTER all iterations of
  			       // forEach have been called back
});