gistfile1.txt

var Parallel = exports.Parallel = function Parallel(actions) {
  if ('object' === typeof actions) {
    var keys = Object.keys(actions);
    for (var i = 0, key; key = keys[i++]; ) {
      this.add(key, actions[key]);
    }
  }
  return this;
};

Parallel.prototype.actions = {};

Parallel.prototype.add = function add(name, action) {
  this.actions[name] = actions;
};

Parallel.prototype.run = function run(callback) {
  var count = 0,
      action,
      args,
      keys = Object.keys(this.actions);

  for (var i = 0, key; key = keys[i++]; ) {
    action = this.actions[key][0];
    args = this.actions[key].slice(1);
    args.push((function(name, action) {
      return function() {
        arguments = Array.prototype.slice(arguments);
        arguments.unshift(name);
        callback.apply(global, arguments);

        count--;
        if (0 >= count) {
          callback(null);
        }
      };
    })(key, action));
    count++;
    action.apply(global, args);
  }

  if (0 >= count) {
    callback(null);
  }
};