Better Promise

promise.js

const fs = require('fs');
const http = require('http');

getConfig()
.then(getWeather)
.then(workWithResult)

function getConfig () {
  return new Promise((resolve, reject) => {
    fs.readFile('./config.json', 'utf8', (err, data) => {
      if (err) { reject(err); }
  
      resolve(JSON.parse(data));
    });
  });
}

function getWeather(cfg) {
  var query = Object.keys(cfg.apiData)
  .map(key => [key, cfg.apiData[key]].join('='))
  .join('&');

  return new Promise((resolve, reject) => {
    http.get(`${cfg.apiUrl}?${query}`, res => {
      res.setEncoding('utf8');
      var json = '';
      res.on('data', (chunk) => { json += chunk; });
      res.on('end', () => resolve(json));
    })
    .on('error', reject);
  })
  .then(JSON.parse);
}

function workWithResult(forcast) {
  console.log(forcast);
}