Why real-time matters in Express - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a basic Express server that listens on port 3000.

Express

const express = require('express');
const app = express();
app.get('/', (req, res) => {
  res.send('Hello World!');
});
app.listen([1], () => {
  console.log('Server running');
});

Drag options to blanks, or click blank then click option'

A3000

B8080

C5000

D4000

Attempts:

3 left

💡 Hint

Common Mistakes

Using a port number that is already in use or not standard for local development.

The standard port for local Express servers is often 3000. This code starts the server on port 3000.

2fill in blank

medium

Complete the code to import and use the Socket.IO library for real-time communication.

Express

const http = require('http');
const express = require('express');
const app = express();
const server = http.createServer(app);
const io = require('[1]')(server);

io.on('connection', (socket) => {
  console.log('A user connected');
});

Drag options to blanks, or click blank then click option'

Asocket.io

Bexpress

Chttp

Dws

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'express' or 'http' instead of the real-time library name.

Socket.IO is the library used to enable real-time, bidirectional communication between web clients and servers.

3fill in blank

hard

Fix the error in the code to emit a message to the connected client.

Express

io.on('connection', (socket) => {
  socket.[1]('message', 'Hello everyone!');
});

Drag options to blanks, or click blank then click option'

Aon

Bsend

Cbroadcast

Demit

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'send' which is not a Socket.IO method for events.

Using 'broadcast' incorrectly.

The emit method sends an event with data to the client. Here, it sends a 'message' event.

4fill in blank

hard

Fill both blanks to broadcast a message to all clients except the sender.

Express

io.on('connection', (socket) => {
  socket.[1].[2]('message', 'Hello others!');
});

Drag options to blanks, or click blank then click option'

Abroadcast

Bemit

Csend

Don

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'send' instead of 'emit'.

Not using 'broadcast' to exclude the sender.

Using socket.broadcast.emit sends a message to all clients except the one that sent it.

5fill in blank

hard

Fill all three blanks to set up a server that listens on port 4000 and sends a welcome message on connection.

Express

const express = require('express');
const http = require('http');
const app = express();
const server = http.createServer(app);
const io = require('[1]')(server);

io.on('connection', ([2]) => {
  [2].emit('welcome', 'Welcome to the real-time server!');
});

server.listen([3], () => {
  console.log('Server listening on port 4000');
});

Drag options to blanks, or click blank then click option'

Asocket.io

Bsocket

C4000

Dexpress

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'express' instead of 'socket.io' for the first blank.

Using wrong variable name for the connection.

Wrong port number.

This code imports Socket.IO, names the connection parameter 'socket', and listens on port 4000.