Bluebird .each vs .mapSeries vs .map

bb.js

var Promise = require('bluebird');

var funcs = Promise.resolve([500, 100, 400, 200].map((n) => makeWait(n)));

funcs
  .each(iterator)       // logs: 500, 100, 400, 200
  .then(console.log)    // logs: [ [Function], [Function], [Function], [Function] ]

funcs
  .mapSeries(iterator)  // logs: 500, 100, 400, 200
  .then(console.log)    // logs: [500, 100, 400, 200]

funcs
  .map(iterator)        // logs: 100, 200, 400, 500
  .then(console.log)    // logs: [500, 100, 400, 200]

function iterator(f) {
  return f()
}

function makeWait(time) {
  return function () {
    return new Promise((resolve, reject) => {
      setTimeout(() => {
        console.log(time);
        resolve(time);
      }, time);
    });
  };
}