//to run : node filename.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}`))
//visit localhost:3000
// assuming you have done 1) npm init 2) npm install 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 on port ${port}`)
})

const express = require('express')const app = express() app.get('/', function (req, res) {  res.send('Hello World')}) app.listen(3000)

const http = require('http');
const app = require('./app');
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 || '3000');
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 'EACCES': 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);