GET route handling in Express - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a GET route for the path '/hello'.

Express

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

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

Aget

Bpost

Cput

Ddelete

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'post' instead of 'get' for a GET route.

Using 'put' or 'delete' which are for other HTTP methods.

The get method defines a route that responds to GET requests.

2fill in blank

medium

Complete the code to send a JSON response with a message in the GET route.

Express

app.get('/json', (req, res) => {
  res.[1]({ message: 'Hello JSON' });
});

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

Aredirect

BsendFile

Crender

Djson

Attempts:

3 left

💡 Hint

Common Mistakes

Using sendFile which sends a file, not JSON.

Using render which is for templates.

The json method sends a JSON response to the client.

3fill in blank

hard

Fix the error in the GET route that tries to access a URL parameter.

Express

app.get('/user/:id', (req, res) => {
  const userId = req.params.[1];
  res.send(`User ID is ${userId}`);
});

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

Auserid

Bid

Cparam

DuserId

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different name than the URL parameter.

Trying to access req.param instead of req.params.

The URL parameter is named 'id', so access it with req.params.id.

4fill in blank

hard

Fill both blanks to create a GET route that sends a status code and a JSON message.

Express

app.[1]('/status', (req, res) => {
  res.status([2]).json({ message: 'All good' });
});

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

Aget

Bpost

C404

D200

Attempts:

3 left

💡 Hint

Common Mistakes

Using POST method instead of GET.

Using 404 status code which means not found.

Use get for GET route and 200 for successful status code.

5fill in blank

hard

Fill all three blanks to create a GET route that reads a query parameter and sends it back in JSON.

Express

app.[1]('/search', (req, res) => {
  const term = req.query.[2];
  res.[3]({ searchTerm: term });
});

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

Aget

Bquery

Cjson

Dparams

Attempts:

3 left

💡 Hint

Common Mistakes

Using params instead of query for query parameters.

Using send instead of json for JSON response.

The route uses get, reads query parameter query, and sends JSON response.

Practice

1. What does the app.get() method do in an Express app?

easy

A. Starts the Express server and listens on a port

B. Defines a route to handle GET requests at a specific URL

C. Sends a POST request to a server

D. Deletes a route from the Express app

Solution

1. Step 1: Understand the purpose of app.get()

   The app.get() method is used to define a route that listens for GET requests on a given URL path.

2. Step 2: Compare with other methods

   Other methods like app.post() handle POST requests, and app.listen() starts the server, so they do not define GET routes.

3. Final Answer:

   Defines a route to handle GET requests at a specific URL -> Option B

4. Quick Check:

   app.get() defines GET routes [OK]

Hint: app.get() always sets up a GET route handler [OK]

Common Mistakes:

• Confusing app.get() with app.listen()
• Thinking app.get() sends requests instead of handling them
• Mixing GET with POST methods

2. Which of the following is the correct syntax to create a GET route for the path /hello that sends "Hello World" as a response?

easy

A. app.get('/hello', (req, res) => { res.send('Hello World'); });

B. app.get('/hello', (res, req) => { res.send('Hello World'); });

C. app.get('/hello', (req, res) => { res.write('Hello World'); });

D. app.get('/hello', (req, res) => { res.sendHello('Hello World'); });

Solution

1. Step 1: Check parameter order in callback

   The callback function parameters must be req first, then res. app.get('/hello', (res, req) => { res.send('Hello World'); }); reverses them, which is incorrect.

2. Step 2: Verify response method usage

   The correct method to send a response string is res.send(). app.get('/hello', (req, res) => { res.write('Hello World'); }); uses res.write() which is not standard in Express, and app.get('/hello', (req, res) => { res.sendHello('Hello World'); }); uses a non-existent method res.sendHello().

3. Final Answer:

   app.get('/hello', (req, res) => { res.send('Hello World'); }); -> Option A

4. Quick Check:

   Correct syntax uses req, res and res.send() [OK]

Hint: Use (req, res) and res.send() to respond in GET routes [OK]

Common Mistakes:

• Swapping req and res parameters
• Using res.write() instead of res.send()
• Calling non-existent response methods

3. What will be the output when a GET request is made to /user/42 with this route handler?

app.get('/user/:id', (req, res) => {
  res.send(`User ID is ${req.params.id}`);
});

medium

A. User ID is undefined

B. User ID is :id

C. Error: req.params is not defined

D. User ID is 42

Solution

1. Step 1: Understand route parameters

   The route /user/:id captures the part after /user/ as req.params.id.

2. Step 2: Substitute parameter in response

   When visiting /user/42, req.params.id is "42", so the response is "User ID is 42".

3. Final Answer:

   User ID is 42 -> Option D

4. Quick Check:

   Route params fill req.params.id correctly [OK]

Hint: Use req.params to get URL parts in routes [OK]

Common Mistakes:

• Using req.params without defining route parameter
• Expecting literal ':id' in output
• Forgetting to use backticks for template strings

4. Identify the error in this GET route handler:

app.get('/data', (req, res) => {
  res.send('Data received')
  res.send('Another response');
});

medium

A. Missing semicolon after first res.send()

B. Route path should be '/data/' with trailing slash

C. Cannot call res.send() twice in the same request handler

D. req parameter is unused and causes error

Solution

1. Step 1: Check response sending rules

   Express allows sending only one response per request. Calling res.send() twice causes an error.

2. Step 2: Analyze other options

   Missing semicolons do not cause runtime errors here, trailing slash is optional, and unused parameters do not cause errors.

3. Final Answer:

   Cannot call res.send() twice in the same request handler -> Option C

4. Quick Check:

   Only one res.send() per request allowed [OK]

Hint: Send response only once per route handler [OK]

Common Mistakes:

• Calling res.send() multiple times
• Thinking missing semicolons cause errors
• Confusing trailing slash necessity

5. You want to create a GET route /product/:category/:id that responds with a message like "Category: electronics, ID: 123". Which code correctly implements this?

hard

A. app.get('/product/:category/:id', (req, res) => { res.send(`Category: ${req.params.category}, ID: ${req.params.id}`); });

B. app.get('/product/:category/:id', (req, res) => { res.send('Category: req.params.category, ID: req.params.id'); });

C. app.get('/product/:category/:id', (res, req) => { res.send(`Category: ${req.params.category}, ID: ${req.params.id}`); });

D. app.get('/product/:category/:id', (req, res) => { res.send(`Category: ${req.query.category}, ID: ${req.query.id}`); });

Solution

1. Step 1: Use correct parameter order and template literals

   The callback must have (req, res) and use backticks with ${} to insert variables. app.get('/product/:category/:id', (req, res) => { res.send(`Category: ${req.params.category}, ID: ${req.params.id}`); }); does this correctly.

2. Step 2: Use req.params for URL parameters

   Route parameters are accessed via req.params, not req.query. app.get('/product/:category/:id', (req, res) => { res.send(`Category: ${req.query.category}, ID: ${req.query.id}`); }); incorrectly uses req.query. app.get('/product/:category/:id', (req, res) => { res.send('Category: req.params.category, ID: req.params.id'); }); uses quotes, so variables won't be evaluated. app.get('/product/:category/:id', (res, req) => { res.send(`Category: ${req.params.category}, ID: ${req.params.id}`); }); swaps parameters.

3. Final Answer:

   app.get('/product/:category/:id', (req, res) => { res.send(`Category: ${req.params.category}, ID: ${req.params.id}`); }); -> Option A

4. Quick Check:

   Use req.params and template literals correctly [OK]

Hint: Use req.params and backticks for dynamic route responses [OK]

Common Mistakes:

• Swapping req and res parameters
• Using string quotes instead of template literals
• Using req.query instead of req.params for route params