Bluebird .mapSeries vs .map

bb.js

var Promise = require('bluebird');

var funcs = Promise.resolve([100, 200, 300, 400].map((n) => makeWait(n)));

console.log('first with {concurrency: 1}');
funcs
  .map(iterator, {concurrency: 1})
  .then(function(r) { console.log('Resolved with', r) } )
  .then(function() {
    console.log('then with mapSeries');
    funcs
      .mapSeries(iterator)
      .then(function(r) { console.log('Resolved with', r) } )
  })

function iterator(f) {
  return f()
}

function makeWait(time) {
  return function () {
    return new Promise((resolve, reject) => {
      console.log('Starting to wait for', time);
      setTimeout(() => {
        console.log('Waited for', time);
        resolve(time);
      }, time);
    });
  };
}

// OUTPUT:
// first with {concurrency: 1}
// Starting to wait for 100
// Waited for 100
// Starting to wait for 400
// Waited for 400
// Starting to wait for 300
// Waited for 300
// Starting to wait for 200
// Waited for 200
// Resolved with [ 100, 200, 300, 400 ]
// then with mapSeries
// Starting to wait for 100
// Waited for 100
// Starting to wait for 200
// Waited for 200
// Starting to wait for 300
// Waited for 300
// Starting to wait for 400
// Waited for 400
// Resolved with [ 100, 200, 300, 400 ]

PERFECT EXAMPLE ❤️ 💖