A try to implement event based flow in javascript

phone-call.js

var EventEmitter = require('events').EventEmitter;

var util = require('util');

var log = function(str){
  var t = Date.now();
  console.log(t + " " + str);
}

var Call = function (){
  var _ = this;
  this.promises = [];
  this.connected = false;

  this.on('remote.hangup', function (e){
    this.connected = false;
    log("Remote hangup : disconnected");
  });
};

util.inherits(Call, EventEmitter);

Call.prototype.queue = function (promise)
{
  this.promises.push(promise);
};

Call.prototype.make = function (number){
  log("Connecting to " + number + "...");
  var that = this;
  var delay = parseInt(Math.random() * 1000);
  var action = new Promise(function(resolve, reject){
    setTimeout(function (){
      log("Connected after " + delay + "ms");
      that.connected = true;
      that.uid = 12345;
      resolve(true);
    }, delay);
  });

  this.queue(action);
  return this;
};

Call.prototype.wait = function (delay){
  var action = new Promise(function (resolve, reject){
    setTimeout(function (){
      log("Waited for " + delay + "s");
      resolve(true);
    }, delay * 1000);
  });

  this.queue(action);

  return this;
};

Call.prototype.hangup = function (){
  var that = this;
  Promise.all(this.promises).then(function(){
    if(that.connected === true){
      log("HangUp");
      that.connected = false;
    } else {
      log("\t> NOT CONNECTED");
      throw new Error("NOT CONNECTED");
    }
  });

  return this;
};

Call.prototype.transfertTo = function (to){
  var that = this;
  Promise.all(this.promises).then(function(){
    if(that.connected === true){
      log("HangUp");
    } else {
      log("\t> NOT CONNECTED");
      throw new Error("NOT CONNECTED");
    }
    var action = new Promise(function (resolve, reject){
      log("Transfering #"+ that.uid+ " to " + to);
      setTimeout(function (){
        log("Transfered to " + to);
        resolve(true);
      }, 800);
    });
    that.queue(action);
  });

  return this;
};

Call.prototype.trigger = function (evt){
  this.emit(evt);
};




var c = new Call();

c.make("4411223344")
  .transfertTo("4433445566")
  .wait(2)
  .transfertTo("4415252499")
  .wait(5)
  .hangup();

setTimeout(function (){
  c.trigger('remote.hangup');
}, 10000);