ECMAScript 6 Promise for Node.js

mongoose-promise.js

const Article = require('./models/article');

function getArticles(callback) {
    callback = callback || function () {};
    return new Promise((resolve, reject) => {
        Article.find({}, (err, articles) => {
            if(err) {
                reject(err);
                return callback(err);
            }
            if(!articles) {
                reject(new Error('No articles'));
                return callback(new Error('No articles'));
            }
            resolve(articles);
            return callback(null, articles);
        });
    });
}
getArticles().then((data) => {
    console.log(data);
}, (err) => {
    console.log(err.message);
})

read-package.js

'use strict';

const fs = require('fs');

function readPackage(callback) {
    callback = callback || function () {};
    return new Promise((resolve, reject) => {
        fs.readFile('./package.json', (err, data) => {
            if(err) {
                reject(err);
                return callback(err);
            }
            resolve(data);
            return callback(null, data);
        });
    });
}
readPackage().then((data) => {
    console.log(data);
}, (err) => {
    console.log(err.message);
})
module.exports.readPackage = readPackage;