utils.js

'use strict';

var nextTick;
if (typeof setImmediate === 'function') {
  nextTick = setImmediate;
} else if (typeof process === 'object' && process && process.nextTick) {
  nextTick = process.nextTick;
} else {
  nextTick = function (cb) {
    setTimeout(cb, 0);
  };
}

function nodeify(promise, cb) {
  if (typeof cb !== 'function') {
    return promise;
  }

  return promise
    .then(function (res) {
      nextTick(function () {
        cb(null, res);
      });
    })
    .catch(function (err) {
      cb(err);
    });
}
function nodeifySelf(cb) {
  return nodeify(this, cb);
}

Object.assign(Promise.prototype, {
  nodeify: nodeifySelf
});

const co = function (genfun) {
  const gen  = genfun();
  const next = (value) => {
    const ret = gen.next(value);
    if (ret.done) return;
    ret.value((err, val) => {
      if (err) { return console.error(err); }
      next(val);
    });
  };
  next();
};

exports.nodeify = nodeify;
exports.co      = co;