Error-handling middleware in Express - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define an error-handling middleware in Express.

Express

app.use(function(err, req, res, [1], next) {
  res.status(500).send('Something broke!');
});

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

Ares

Berror

Cnext

Drequest

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'res' or 'request' as the fourth parameter instead of 'next'.

Omitting the fourth parameter entirely.

The error-handling middleware in Express must have four parameters: err, req, res, and next. The next parameter is required to identify it as error-handling middleware.

2fill in blank

medium

Complete the code to send a JSON error response with status 400.

Express

app.use(function(err, req, res, next) {
  res.status([1]).json({ error: err.message });
});

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

A400

B200

C404

D500

Attempts:

3 left

💡 Hint

Common Mistakes

Using 200 which means success.

Using 500 which means server error.

To indicate a client error, the status code 400 is used. This sends a JSON response with the error message.

3fill in blank

hard

Fix the error in the middleware signature to correctly handle errors.

Express

app.use(function(req, res, next, [1]) {
  res.status(500).send('Error occurred');
});

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

Arequest

Berror

Cnext

Derr

Attempts:

3 left

💡 Hint

Common Mistakes

Placing the error parameter last instead of first.

Using wrong parameter names or order.

The error-handling middleware must have the error parameter err as the first argument, followed by req, res, and next. The order matters.

4fill in blank

hard

Fill both blanks to correctly pass the error to the next middleware.

Express

app.use(function(err, req, res, [1]) {
  if (err) {
    [2](err);
  } else {
    next();
  }
});

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

Anext

Bres

Csend

Derror

Attempts:

3 left

💡 Hint

Common Mistakes

Using res or send instead of next.

Not calling next with the error.

The next function is used to pass control to the next middleware. Calling next(err) passes the error along the middleware chain.

5fill in blank

hard

Fill all three blanks to create a middleware that logs the error and sends a 500 response.

Express

app.use(function([1], req, res, [2]) {
  console.error([3]);
  res.status(500).send('Server error');
});

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

Aerr

Bnext

Derror

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up parameter names.

Not logging the error correctly.

The error parameter is named err and the next middleware function is next. Logging the error uses console.error(err).