series-async.js

'use strict';

function asyncTask(data, callback) {
  process.setTimeout(function process() {
    return callback(null, 'processed ' + data);
  }, 100);
}

function doLotsOfStuff(callback) {
  var tasks = ['task1', 'task2', 'task3'];
  var results = [];
  function checkForTasks() {
    if (!tasks.length) {
      return callback(results);
    }
    asyncTask(tasks.shift(), function doneWithOneTask(result) {
      results.push(result);
      checkForTasks();
    });
  }
  checkForTasks();
}

doLotsOfStuff(function done() {
  console.log('done with lots of stuff');
});