Handling connection events in Express - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a connection event in Express?

A connection event in Express is an event triggered when a client connects to the server, allowing the server to respond or log the connection.

intermediate

How do you listen for connection events in an Express app?

You listen for connection events by attaching event listeners to the server object returned by app.listen(), for example using server.on('connection', callback).

beginner

What object do you use to handle connection events in Express?

You use the HTTP server object returned by app.listen() to handle connection events, not the Express app object itself.

intermediate

Why might you want to handle connection events in an Express app?

Handling connection events helps monitor active connections, log client activity, or manage resources like sockets for better server control.

beginner

Show a simple example of handling a connection event in Express.

const express = require('express');
const app = express();
const server = app.listen(3000);
server.on('connection', (socket) => {
  console.log('New client connected');
});

Which object do you attach a 'connection' event listener to in Express?

A The Express app object

B The response object

C The request object

D The server object returned by app.listen()

The 'connection' event is emitted by the server object returned by app.listen(), not by the Express app or request/response objects.

What does the 'connection' event provide as an argument to its callback?

A A socket object representing the client connection

B The HTTP request object

C The Express app instance

D The server configuration

The 'connection' event callback receives a socket object that represents the client connection.

Why is handling connection events useful in an Express server?

A To monitor and manage client connections

B To handle HTTP request routing

C To serve static files

D To parse JSON bodies

Handling connection events helps monitor and manage client connections, which is different from routing or parsing requests.

Which method starts the Express server and returns the server object?

A app.start()

B app.listen()

C express.createServer()

D server.connect()

app.listen() starts the server and returns the server object used to listen for connection events.

Can you listen for 'connection' events directly on the Express app object?

A Only if you use middleware

B Yes, the app object emits connection events

C No, you must listen on the server object

D Only in Express version 5+

The Express app object does not emit 'connection' events; you must listen on the server object returned by app.listen().

Explain how to handle connection events in an Express server and why it might be useful.

Think about the server object and what happens when a client connects.

Describe the difference between the Express app object and the server object regarding connection events.

Consider which object deals with network connections.