Comparison between different ways to implement async methods in Node.js

async-comparison.js

'use strict';

const async = require('async');
const Promise = require('bluebird');

const db = {
  app: [
    { id: 10, name: 'twitter' },
    { id: 11, name: 'facebook' },
    { id: 12, name: 'google' }
  ],
  user: [
    { id: 20, name: 'Alejandro', age: 24 },
    { id: 21, name: 'James', age: 26 },
    { id: 22, name: 'Kevin', age: 28 }
  ],
  _indexes: {
    app: {
      10: 0,
      11: 1,
      12: 2
    },
    user: {
      20: 0,
      21: 1,
      22: 2
    }
  }
};

const APP_ID = 10;
const USER_ID = 20;

// Async functions using promises and callbacks

function getApp(id) {
  return new Promise((resolve, reject) => {
    var index = db._indexes.app[id];
    setTimeout(_ => {
      if (index !== undefined) {
        resolve(db.app[index]);
      } else {
        reject(new Error('App not found'));
      }
    }, 50);
  });
}

function getUser(id) {
  return new Promise((resolve, reject) => {
    var index = db._indexes.user[id];
    setTimeout(_ => {
      if (index !== undefined) {
        resolve(db.user[index]);
      } else {
        reject(new Error('User not found'));
      }
    }, 50);
  });
}

function getAppCb(id, cb) {
  var index = db._indexes.app[id];
  setTimeout(_ => {
    if (index !== undefined) {
      cb(null, db.app[index]);
    } else {
      cb(new Error('App not found'));
    }
  }, 50);
}

function getUserCb(id, cb) {
  var index = db._indexes.user[id];
  setTimeout(_ => {
    if (index !== undefined) {
      cb(null, db.user[index]);
    } else {
      cb(new Error('User not found'));
    }
  }, 50);
}

// Async code handlers

var coroutine = Promise.coroutine(function* () {
  try {
    var app = yield getApp(APP_ID);
    var user = yield getUser(USER_ID);
    console.log('coroutine:', app, user);
  } catch(e) {
    console.error('coroutine:', e); 
  }
});

function promises() {
  getApp(APP_ID).then(app => {
    getUser(USER_ID).then(user => {
      console.log('promises:', app, user);
    }).catch(err => console.error('promises:', err));
  }).catch(err => console.error('promises:', err));
}

function callbacks() {
  getAppCb(APP_ID, (err, app) => {
    if (err) { console.error('callbacks:', err); return; }
    getUserCb(USER_ID, (err, user) => {
      if (err) { console.error('callbacks:', err); return; }
      console.log('callbacks:', app, user);
    });
  });
}

function asyncSeries() {
  async.series({
    app: cb => getAppCb(APP_ID, cb),
    user: cb => getUserCb(USER_ID, cb)
  }, (err, result) => {
    if (err) { console.error('asyncSeries:', err); return; }
    console.log('asyncSeries:', result.app, result.user);
  });
}

coroutine();
promises();
callbacks();
asyncSeries();