Promise.all for parallel; this for series

sequence-promises.js

'use strict';
var Promise = require('es6-promise');

// See http://www.html5rocks.com/en/tutorials/es6/promises/
module.exports = function sequencePromises (promises, transformFn) {
  function identity (x) { return x; }

  return promises.reduce(function (sequence, promise) {
    return sequence.then(function () {
      return promise;
    }).then((typeof transformFn === 'function') ? transformFn : identity);
  }, Promise.resolve());
};