express documentation node js code example

Example 1: node.js express

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}`))

Example 2: express and node

// Load HTTP module
const http = require("http");

const hostname = "127.0.0.1";
const port = 8000;

// Create HTTP server 
const server = http.createServer((req, res) => {

   // Set the response HTTP header with HTTP status and Content type
   res.writeHead(200, {'Content-Type': 'text/plain'});
   
   // Send the response body "Hello World"
   res.end('Hello World\n');
});

// Prints a log once the server starts listening
server.listen(port, hostname, () => {
   console.log(`Server running at http://${hostname}:${port}/`);
})

Example 3: node js 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 }`));

Example 4: what is express.js

Express is a minimal and flexible Node.js web application framework
that provides a robust set of features for web and mobile
applications.