server.js

const http = require('http')
const app = require('./app')
const dotenv = require('dotenv').config()

const normalizePort = val => {
    const port = parseInt(val, 10)

    if(isNaN(port)) {
        return val
    }
    if (port >=0) {
        return port
    }
    return false
}

const port = normalizePort(process.env.PORT)
app.set('port', port)

const errorHandler = error => {
    if(error.syscall !== 'listen') {
        throw error
    }
    const address = server.address()
    const bind = typeof address === 'string' ? 'pipe' + address : 'port' + port
    switch (error.code) {
        case 'EACCESS':
            console.error(bind + 'requires elevated privileges.')
            process.exit(1)
            break
        case 'EADDRINUSE':
            console.error(bind+ 'is already in use.')
            process.exit(1)
            break
        default : 
        throw error
    }
}

const server = http.createServer(app)

server.on('error', errorHandler)
server.on('listening', () => {
    const address = server.address()
    const bind = typeof address === 'string'? 'pipe' + address : 'port' + port
    console.log('Listening on' + bind)
})

server.listen(port)