await-then-promise-return.js

var Promise = require('bluebird');

function returnTimedPromise (timer) {
  return new Promise((resolve, reject) => {
    setTimeout(resolve, timer)
  })
}

counters = [...Array(10).keys()];

var dt = new Date();

Promise.mapSeries(counters, async(counter) => {
  await returnTimedPromise((counter + 1) * 1000);
  return returnTimedPromise(3000);
}).then(r => {
  console.log(`Finished after ${((new Date()) - dt)/1000} seconds`)
})

// Finished after 85.44 seconds

nested-promise-return.js

var Promise = require('bluebird');

function returnTimedPromise (timer) {
  return new Promise((resolve, reject) => {
    setTimeout(resolve, timer)
  })
}

counters = [...Array(10).keys()];

var dt = new Date();

Promise.mapSeries(counters, async(counter) => {
  return returnTimedPromise((counter + 1) * 1000)
    .then(() => {
      returnTimedPromise(3000)
    });
}).then(r => {
  console.log(`Finished after ${((new Date()) - dt)/1000} seconds`)
})

//  Finished after 56.456 seconds