expressjs

                                    var express = require('express')
var app = express()

                                    // node js -> express -> basic example: static folder, 404 page

const express = require('express');
const path = require('path');
const PORT = process.env.PORT || 5000;

const app = express();

function error404(req, res) {
  res.status(404);

  if (req.accepts('html')) {
    res.sendFile(path.join(__dirname, 'public/errors/404.html'));
    return;
  }

  if (req.accepts('json')) {
    res.send({
      status: 404,
      error: 'Not found'
    });
    return;
  }
  
  res.type('txt').send('404 - Not found');
}

app
  .use(express.static(path.join(__dirname, 'public')))
  .use(error404)
  .listen(PORT, () => console.log(`Listening on ${ PORT }`));

                                    
const express = require('express')
const app = express()
const port = 3000

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

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

                                    Express.js, or simply Express, is a web application framework for Node.js,
released as free and open-source software under the MIT License.

It is designed for building web applications and APIs.
It has been called the de facto standard server framework for Node.js.

                                    
const express = require('express')
const app = express()
const port = 3000

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

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