gistfile1.js

// Inspired by http://www.dustindiaz.com/async-method-queues
// also helpful http://www.mattgreer.org/articles/promises-in-wicked-detail/
function Queue() {
  this._methods = [];
  this._flushing = false;
}

Queue.prototype = {
  add: function(fn) {
    this._methods.push(fn);
    if (!this._flushing) {
      this.step();
    }
  },

  step: function(resp) {
    var self = this;

    if (!this._flushing) {
      this._flushing = true;
    }
    
    function executeInPromise (fn) {
      return new Promise(function (resolve, reject) {
        if (fn) {
          var ret = fn();
        }
        resolve(ret);
      });
    }

    executeInPromise(this._methods.shift()).then(function (resolve) {
      if (self._methods.length > 0) {
        self.step();
      }
    })
  }
};



function Test () {
  this.letter = 'a';
  this.queue = new Queue;
}

Test.prototype.asyncMethod = function (letter) {
  var self = this;
  this.queue.add(function() {
    console.log('async start time ' + Date.now());
    return new Promise(function (resolve, reject) {
      setTimeout(function () {
        self.letter = letter;
        console.log('async end time ' + Date.now());
        resolve();
      }, 1000)
    })
  });
  return this;
};

Test.prototype.syncMethod = function (letter) {
  var self = this;
  this.queue.add(function () {
    console.log('sync start time ' + Date.now());
    self.letter = letter;
    console.log('sync end time ' + Date.now());
  })
  return this;
};

var test = new Test;
test.asyncMethod('b').asyncMethod('c').syncMethod('d').asyncMethod('e').syncMethod('f')