Promise Sequential.js

var T = function (id) {

  var p = new Promise(function (resolve) {
    setTimeout(function () {
      console.log(id, 'resolved');
      resolve(id);
    }, Math.random()*3000);
  });

  return p;

};

var arr = [T('1'), T('2'), T('3'), T('4'), T('5')];

var f = function (id) {
  console.log(id, 'parsed');	
};

var sequential = function (f) {
  return function (prev, curr) {
    var p = Promise.all([curr, prev]);
    p.then(function (args) { f(args[0]); });
    return p.then(function (args) {
      return args[1].concat(args[0]);
    });
  };
};


/*var sequential2 = function (f) {
  return function (prev, curr) {
    return Promise.all([curr, prev]).then(function (args) {
      f(args[0]);
      return args[1].concat(args[0]);
    });
  };
};*/


var all = arr.reduce(sequential(f), Promise.resolve([]));

all.then(function () {
  console.log('all done');
  console.log(arguments);
});