A better co example

codemo.js

'use strict';

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

co(function* () {
  let readFile = (resolve, reject) => {
    fs.readFile('./codemo.js', { encoding : 'utf-8' }, function(err, content) {
      if (err) {
        return reject(err);
      }
      
      resolve(content);
  });
};


  var res = yield [
    new Promise(readFile),
    Promise.resolve(1),
    Promise.resolve(2),
    Promise.resolve(3),
  ];

  console.log('res1', res);

  var res2 = yield [
    new Promise(readFile),
    Promise.resolve(1),
    Promise.resolve(2),
    Promise.resolve(3),
  ];

  console.log('res2 - always executed after res1', res2);
}).catch(onerror);

function onerror(err) {
  console.log(err);
}