• index.js - Main file where we have imported express and defined the routes
• services/MainService.js - ES6 Class with one method get() which handles the route /
• app.js - Here happens the magic in-order to enable importing the ES6 Classes using import keyword

Instead of doing

var express = require("express");

We have used import keyword

import express from 'express';

Importing the MainService Class import MainService from './services/MainService'; from the index.js