Basic Express Boilerplate

app.js

require('dotenv').config()
const express = require('express')
const morgan = require('morgan')
const cors = require('cors')
const helmet = require('helmet')
const { NODE_ENV } = require('./config')

const app = express()

const morganOption = (NODE_ENV === 'production')
  ? 'tiny'
  : 'common';

app.use(morgan(morganOption))
app.use(cors())
app.use(helmet())

app.get('/', (req, res) => {
    res.send('Hello, world!')
})

  app.use(function errorHandler(error, req, res, next) {
      let response
      if (NODE_ENV === 'production') {
        response = { error: { message: 'server error' } }
      } else {
        console.error(error)
        response = { message: error.message, error }
      }
      res.status(500).json(response)
    })

module.exports = app

config.js

module.exports = {
    PORT: process.env.PORT || 8000,
    NODE_ENV: process.env.NODE_ENV || 'development',
}

package.json

{
  "name": "express-boilerplate",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "mocha --require test/setup.js",
    "dev": "nodemon src/server.js",
    "start": "node src/server.js",
    "predeploy": "npm audit",
    "deploy": "git push heroku master"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "dependencies": {
    "cors": "^2.8.5",
    "dotenv": "^6.2.0",
    "express": "^4.16.4",
    "helmet": "^3.15.0",
    "morgan": "^1.9.1"
  },
  "devDependencies": {
    "chai": "^4.2.0",
    "mocha": "^5.2.0",
    "nodemon": "^1.18.9",
    "supertest": "^3.4.1"
  }
}

server.js

const app = require('./app')
const { PORT } = require('./config')

app.listen(PORT, () => {
  console.log(`Server listening at http://localhost:${PORT}`)
})