DELETE route handling in Express - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a DELETE route for '/items/:id'.

Express

app.[1]('/items/:id', (req, res) => {
  res.send('Delete item ' + req.params.id);
});

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

Adelete

Bget

Cput

Dpost

Attempts:

3 left

💡 Hint

Common Mistakes

Using app.get instead of app.delete

Using app.post or app.put for delete routes

The DELETE method is used to handle delete requests in Express. Use app.delete to define a DELETE route.

2fill in blank

medium

Complete the code to extract the 'id' parameter from the DELETE route.

Express

app.delete('/items/:id', (req, res) => {
  const itemId = req.[1].id;
  res.send('Deleting item ' + itemId);
});

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

Abody

Bquery

Cheaders

Dparams

Attempts:

3 left

💡 Hint

Common Mistakes

Using req.body to get route parameters

Using req.query for route parameters

Route parameters like ':id' are accessed via req.params in Express.

3fill in blank

hard

Fix the error in the DELETE route to send a 204 status code with no content.

Express

app.delete('/users/:userId', (req, res) => {
  // Delete user logic here
  res.[1](204).send();
});

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

AsendStatus

Bstatus

Cjson

Dend

Attempts:

3 left

💡 Hint

Common Mistakes

Using res.sendStatus(204) which ends the response and cannot be chained with .send()

Using res.json() which sends a JSON body

To send a status code with no content, use res.status(204).send(). The sendStatus method sends the status and ends the response (with empty body for 204).

4fill in blank

hard

Fill both blanks to create a DELETE route that checks if the item exists and sends appropriate status.

Express

app.delete('/products/:id', (req, res) => {
  const id = req.[1].id;
  if (!database.has(id)) {
    return res.[2](404).send('Not found');
  }
  database.delete(id);
  res.status(204).send();
});

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

Aparams

Bbody

Cstatus

DsendStatus

Attempts:

3 left

💡 Hint

Common Mistakes

Using req.body instead of req.params for id

Using res.sendStatus(404) which sends default message without custom text

Use req.params to get the id from the URL. Use res.status(404).send() to send a 404 Not Found status with a message.

5fill in blank

hard

Fill all three blanks to create a DELETE route that validates the id, deletes the item, and sends a JSON response.

Express

app.delete('/tasks/:taskId', (req, res) => {
  const id = req.[1].taskId;
  if (!isValidId(id)) {
    return res.[2](400).json({ error: 'Invalid ID' });
  }
  deleteTask(id);
  res.[3](200).json({ message: 'Task deleted' });
});

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

Aparams

Bstatus

Dbody

Attempts:

3 left

💡 Hint

Common Mistakes

Using req.body instead of req.params for taskId

Using res.send instead of res.json for JSON response

Using res.sendStatus which sends default text instead of JSON

Use req.params to get the taskId. Use res.status(400).json() to send a 400 error with JSON. Use res.status(200).json() to send success message in JSON.

Practice

1. What is the main purpose of a DELETE route in Express?

easy

A. To update existing data on the server

B. To add new data to the server

C. To remove data from the server

D. To retrieve data from the server

Solution

1. Step 1: Understand HTTP methods

   HTTP methods define actions: GET retrieves, POST adds, PUT updates, DELETE removes.

2. Step 2: Identify DELETE route purpose

   DELETE routes specifically handle requests to remove data from the server.

3. Final Answer:

   To remove data from the server -> Option C

4. Quick Check:

   DELETE = remove data [OK]

Hint: DELETE routes always remove data from the server [OK]

Common Mistakes:

• Confusing DELETE with POST or GET
• Thinking DELETE adds or updates data
• Assuming DELETE retrieves data

2. Which of the following is the correct syntax to define a DELETE route for path /items/:id in Express?

easy

A. app.delete('/items/:id', (req, res) => { /* handler */ });

B. app.get('/items/:id', (req, res) => { /* handler */ });

C. app.post('/items/:id', (req, res) => { /* handler */ });

D. app.put('/items/:id', (req, res) => { /* handler */ });

Solution

1. Step 1: Identify HTTP method for deletion

   DELETE method is used to remove resources, so app.delete is correct.

2. Step 2: Check route path and handler syntax

   The path /items/:id with a callback function matches Express route syntax.

3. Final Answer:

   app.delete('/items/:id', (req, res) => { /* handler */ }); -> Option A

4. Quick Check:

   DELETE route syntax = app.delete(path, handler) [OK]

Hint: Use app.delete for DELETE routes, not get/post/put [OK]

Common Mistakes:

• Using app.get or app.post instead of app.delete
• Missing the callback function
• Incorrect path format

3. What will be the response if the following Express DELETE route is called with DELETE /users/5 and the user with id 5 exists?

const users = [{id: 1}, {id: 5}, {id: 9}];
app.delete('/users/:id', (req, res) => {
  const id = Number(req.params.id);
  const index = users.findIndex(u => u.id === id);
  if (index !== -1) {
    users.splice(index, 1);
    res.status(200).send('User deleted');
  } else {
    res.status(404).send('User not found');
  }
});

medium

A. Response status 200 with message 'User deleted'

B. Response status 404 with message 'User not found'

C. Response status 500 with server error

D. Response status 200 with message 'User not found'

Solution

1. Step 1: Check if user with id 5 exists

   The array contains {id: 5}, so index will not be -1.

2. Step 2: Analyze response when user found

   Since index !== -1, user is removed and response status 200 with 'User deleted' is sent.

3. Final Answer:

   Response status 200 with message 'User deleted' -> Option A

4. Quick Check:

   User exists = 200 'User deleted' [OK]

Hint: If item found, DELETE route sends 200 with success message [OK]

Common Mistakes:

• Assuming 404 even if user exists
• Confusing status codes
• Not converting id to number before comparison

4. Identify the error in this DELETE route code snippet:

app.delete('/products/:id', (req, res) => {
  const id = req.params.id;
  const product = products.find(p => p.id === id);
  if (!product) {
    res.status(404).send('Product not found');
  }
  products = products.filter(p => p.id !== id);
  res.send('Product deleted');
});

medium

A. Incorrect route path syntax

B. Missing callback function in app.delete

C. id is not converted to number before comparison

D. res.send called twice without return

Solution

1. Step 1: Check flow after 404 response

   If product not found, res.status(404).send is called but code continues without return.

2. Step 2: Identify multiple responses sent

   After 404 response, code still filters products and calls res.send again, causing error.

3. Final Answer:

   res.send called twice without return -> Option D

4. Quick Check:

   Multiple res.send calls without return cause errors [OK]

Hint: Use return after sending response to avoid multiple sends [OK]

Common Mistakes:

• Not returning after sending 404 response
• Ignoring type conversion for id
• Assuming route path is wrong

5. You want to create a DELETE route that removes a book by its ID from a nested data structure where books are grouped by genre. Which approach correctly handles deletion and sends a 404 if the book is not found?

const library = {
  fiction: [{id: 1, title: 'A'}, {id: 2, title: 'B'}],
  nonFiction: [{id: 3, title: 'C'}]
};

app.delete('/books/:id', (req, res) => {
  const id = Number(req.params.id);
  let found = false;
  for (const genre in library) {
    const index = library[genre].findIndex(book => book.id === id);
    if (index !== -1) {
      library[genre].splice(index, 1);
      found = true;
      break;
    }
  }
  if (found) {
    res.status(200).send('Book deleted');
  } else {
    res.status(404).send('Book not found');
  }
});

hard

A. The code does not break after deletion, causing multiple deletions

B. This code correctly deletes the book and handles 404 if not found

C. The code misses converting id to number, causing no matches

D. The code sends 200 status even if book is not found

Solution

1. Step 1: Check id conversion

   id is converted to Number, ensuring correct comparison with book ids.

2. Step 2: Verify loop and deletion logic

   Loop checks each genre, finds book by id, deletes it, sets found true, and breaks loop to avoid extra deletions.

3. Step 3: Confirm response handling

   If found is true, sends 200 with 'Book deleted'; else sends 404 with 'Book not found'.

4. Final Answer:

   This code correctly deletes the book and handles 404 if not found -> Option B

5. Quick Check:

   Proper id conversion, deletion, and response = correct code [OK]

Hint: Convert id, break loop after deletion, send 404 if not found [OK]

Common Mistakes:

• Not converting id to number before comparison
• Not breaking loop after deletion
• Sending success response even if book missing