Express installation and setup - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import Express in your Node.js file.

Express

const express = require([1]);

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

A"express"

B"node"

C"http"

D"fs"

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting the quotes around the package name.

Using a wrong package name like 'http' or 'fs'.

You need to require the express package by its name as a string to use it in your file.

2fill in blank

medium

Complete the code to create an Express app instance.

Express

const app = [1]();

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

Aapp

Bhttp

Crequire

Dexpress

Attempts:

3 left

💡 Hint

Common Mistakes

Trying to call 'http()' instead of 'express()'.

Using 'app()' before defining it.

Calling express() creates a new Express application.

3fill in blank

hard

Fix the error in the code to start the server on port 3000.

Express

app.listen([1], () => {
  console.log('Server running on port 3000');
});

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

A3000

Bapp

C"3000"

Dexpress

Attempts:

3 left

💡 Hint

Common Mistakes

Passing the port as a string instead of a number.

Passing the app or express instead of a port number.

The port number should be a number, not a string, when passed to listen.

4fill in blank

hard

Fill both blanks to create a GET route for the home page that sends 'Hello World!'.

Express

app.[1]('[2]', (req, res) => {
  res.send('Hello World!');
});

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

Aget

Bpost

C/

D/home

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'post' instead of 'get' for a simple page load.

Using '/home' instead of '/' for the main page.

The get method defines a GET route, and '/' is the root path for the home page.

5fill in blank

hard

Fill all three blanks to import Express, create an app, and start the server on port 5000.

Express

const [1] = require('[2]');
const app = [3]();
app.listen(5000, () => {
  console.log('Server started on port 5000');
});

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

Aexpress

Dhttp

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'http' instead of 'express' for import.

Calling 'http()' instead of 'express()'.

You import the 'express' package, assign it to a variable named 'express', then call it to create the app.

Practice

1. What command do you use to install Express in a Node.js project?

easy

A. npm install express

B. node install express

C. express install

D. npm start express

Solution

1. Step 1: Understand Node.js package installation

   Node.js packages are installed using the npm tool with the command npm install <package-name>.

2. Step 2: Identify the correct package name for Express

   The package name for Express is exactly "express", so the command is npm install express.

3. Final Answer:

   npm install express -> Option A

4. Quick Check:

   Express installation command = npm install express [OK]

Hint: Use npm install followed by package name [OK]

Common Mistakes:

• Using 'node install' instead of 'npm install'
• Typing 'express install' which is invalid
• Trying to start express with npm start express

2. Which of the following is the correct way to import Express and create an app instance?

easy

A. const express = require('express'); const app = express();

B. import express from 'express'; const app = express();

C. const app = require('express'); app = express();

D. const express = import('express'); const app = express();

Solution

1. Step 1: Recognize CommonJS import syntax

   In many Node.js projects, Express is imported using CommonJS syntax: const express = require('express');.

2. Step 2: Create app instance correctly

   After importing, the app instance is created by calling express(), so const app = express(); is correct.

3. Final Answer:

   const express = require('express'); const app = express(); -> Option A

4. Quick Check:

   Import Express and create app = require + express() [OK]

Hint: Use require('express') then call express() [OK]

Common Mistakes:

• Using import without proper module setup
• Calling require('express')() directly without variable
• Using import as a function

3. What will the following code do when run?

const express = require('express');
const app = express();
app.get('/', (req, res) => res.send('Hello World'));
app.listen(3000, () => console.log('Server started'));

medium

A. Start a server but does not respond to any requests

B. Throw an error because app.listen is missing a callback

C. Respond with 'Hello World' without starting a server

D. Start a server on port 3000 that responds with 'Hello World' at root URL

Solution

1. Step 1: Analyze server setup and route

   The code creates an Express app, sets a GET route for '/' that sends 'Hello World'.

2. Step 2: Understand app.listen behavior

   The server listens on port 3000 and logs 'Server started' when ready, so it starts correctly.

3. Final Answer:

   Start a server on port 3000 that responds with 'Hello World' at root URL -> Option D

4. Quick Check:

   Express server with route '/' = Hello World response [OK]

Hint: app.listen starts server; app.get defines response [OK]

Common Mistakes:

• Thinking app.listen needs a callback to work
• Assuming no response because of missing middleware
• Confusing route setup with server start

4. Identify the error in this Express setup code:

const express = require('express');
const app = express;
app.listen(3000);

medium

A. app.listen needs a callback function

B. Missing parentheses when creating app instance

C. express should be imported with import, not require

D. app.listen requires a port number as a string

Solution

1. Step 1: Check app instance creation

   The code assigns app = express without calling it. It should be express() to create the app instance.

2. Step 2: Verify app.listen usage

   Calling app.listen(3000) is correct; port number is a number, and callback is optional.

3. Final Answer:

   Missing parentheses when creating app instance -> Option B

4. Quick Check:

   express() must be called to create app [OK]

Hint: Remember to call express() with parentheses [OK]

Common Mistakes:

• Assigning app = express instead of app = express()
• Passing port as string instead of number (allowed but not required)
• Thinking callback in listen is mandatory

5. You want to create an Express server that listens on port 8080 and responds with 'Welcome!' at the root URL. Which code snippet correctly does this?

hard

A. const express = require('express'); const app = express(); app.listen(8080, () => console.log('Server running'));

B. const express = require('express'); const app = express; app.get('/', (req, res) => res.send('Welcome!')); app.listen(8080);

C. const express = require('express'); const app = express(); app.get('/', (req, res) => res.send('Welcome!')); app.listen(8080);

D. const express = require('express'); const app = express(); app.get('/', (req, res) => res.send('Welcome!')); app.listen('3000');

Solution

1. Step 1: Create app instance correctly

   Use const app = express(); to create the Express app instance.

2. Step 2: Define route and start server on port 8080

   Set up app.get('/', ...) to respond with 'Welcome!' and call app.listen(8080); to start the server.

3. Final Answer:

   const express = require('express'); const app = express(); app.get('/', (req, res) => res.send('Welcome!')); app.listen(8080); -> Option C

4. Quick Check:

   Express app with route and listen on 8080 = const express = require('express'); const app = express(); app.get('/', (req, res) => res.send('Welcome!')); app.listen(8080); [OK]

Hint: Call express(), define route, then listen on port [OK]

Common Mistakes:

• Not calling express() to create app
• Passing port as string instead of number (allowed but inconsistent)
• Starting server without defining route