promisify

index.js

'use strict';

const {
  cbFunction,
  cbFunctionPromisify
} = require('./modules/util');

const dataError = {error: true, message: 'I am an unicorn !!!'};
const dataResult = {error: false, message: 'I am an unicorn !!!'};

cbFunction(dataError, (err, result) => {
  if (err) {
    console.log('cb0 error: ', err);
  }
  console.log('cb0 result', result);
});

cbFunction(dataResult, (err, result) => {
  if (err) {
    console.log('cb1 error: ', err);
  }
  console.log('cb1 result', result);
});

cbFunctionPromisify(dataError)
  .then((result) => {
    console.log('p0 result', result);
  })
  .catch((err) => {
    console.log('p0 error: ', err);
  });

cbFunctionPromisify(dataResult)
  .then((result) => {
    console.log('p1 result', result);
  })
  .catch((err) => {
    console.log('p1 error: ', err);
  });

promisify.js

'use strict';

const {
  promisify
} = require('util');

const cbFunction = (data, cb) => {
  if (data.error === true) {
    return cb('I am a error');
  }
  return cb(null, data.message);
};

const cbFunctionPromisify = promisify(cbFunction);

module.exports = {
  cbFunction,
  cbFunctionPromisify
};