the async.series function, unleashed

asyncSeries

// borrowed from async.js because I dislike promises (very much)
// https://github.com/caolan/async/blob/master/lib/async.js

function _eachSeries(arr, iterator, callback) {
  callback = callback || function () {};
  if (!arr.length) {
    return callback();
  }
  var completed = 0;
  var iterate = function () {
    iterator(arr[completed], function (err) {
      if (err) {
        callback(err);
        callback = function () {};
      }
      else {
        completed += 1;
        if (completed >= arr.length) {
          callback();
        }
        else {
          iterate();
        }
      }
    });
  };
  iterate();
}

function series(tasks, callback) {
  callback = callback || function () {};
  
  var results = {};
  _eachSeries(Object.keys(tasks), function (k, callback) {
    tasks[k](function (err) {
      var args = Array.prototype.slice.call(arguments, 1);
      if (args.length <= 1) {
        args = args[0];
      }
      results[k] = args;
      callback(err);
    });
  }, function (err) {
    callback(err, results);
  });
}