Promise map (Bluebird)

bluebird-concurrent-download-using-map-then.js

const Bluebird = require('bluebird')
const got = require('got')

const urls = [
  "http://www.google.com/",
  "http://www.yahoo.com/",
  "http://www.bing.com/",
];

// Bluebird is an extension of promises:
Bluebird.resolve(urls)
  .map(url => got(url), {concurrency: 4})
  .map(response => response.body)
  .map((html, i) => {
    // Now you can access/parse each response as `html` here, and reshape the value for the next `.then` or `.map`
    return {html: html, url: urls[i]}
  }, {concurrency: 8})