Example of using es6-promise in Node to perform asynchronous API calls.

app.js

var express = require('express');
var Promise = require('es6-promise').Promise;
var http = require('http');

var app = express();

var getJSON = function(options) {
  console.log('CALLING ' + options['host']);
  var promise = new Promise(function(resolve, reject) {
    var req = http.get(options, function(res) {
      console.log('STATUS: ' + res.statusCode);
      console.log('HEADERS: ' + JSON.stringify(res.headers));

      setTimeout(function() {
        // Buffer the body entirely for processing as a whole.
        var bodyChunks = [];
        res.on('data', function(chunk) {
          // You can process streamed parts here...
          bodyChunks.push(chunk);
        }).on('end', function() {
          var body = Buffer.concat(bodyChunks);
          console.log('RETURNING BODY: ' + body);
          resolve(body);
        });
      }, 3000);
    });

    req.on('error', function(e) {
      console.log('RETURNING ERROR: ' + e.message);
      reject(e);
    });
  });
  return promise;
};

app.get('/', function(req, res) {
  var promises = [
    getJSON({ host: 'addressbook-api.herokuapp.com', path: '/contacts.json' }),
    getJSON({ host: 'api.zippopotam.us', path: '/us/90210' })
  ];

  Promise.all(promises).then(function(results) {
    console.log(results);
    res.send('DONE!');
  }).catch(function(reason) {
    console.log(reason);
    res.send(reason);
  });
});

var server = app.listen(8000, function() {
  console.log('Listening on port %d', server.address().port);
});