Middleware execution flow (req, res, next) in Express - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a middleware function that logs the request method.

Express

app.use(function(req, res, [1]) {
  console.log(req.method);
  next();
});

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

Asend

Bnext

Cend

Dhandle

Attempts:

3 left

💡 Hint

Common Mistakes

Using send or end instead of next causes the request to stop.

The next function is used to pass control to the next middleware.

2fill in blank

medium

Complete the code to call the next middleware after logging the URL.

Express

app.use((req, res, [1]) => {
  console.log(req.url);
  [1]();
});

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

Ahandle

Bsend

Cend

Dnext

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting to call next() causes the request to hang.

Calling next() passes control to the next middleware in the stack.

3fill in blank

hard

Fix the error in the middleware to properly pass control to the next function.

Express

app.use(function(req, res, next) {
  console.log('Middleware running');
  [1]();
});

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

Anext

Bsend

Cend

Dhandle

Attempts:

3 left

💡 Hint

Common Mistakes

Writing next; instead of next(); does not call the function.

You must call next() as a function, not just reference it.

4fill in blank

hard

Fill both blanks to create middleware that checks if user is authenticated and calls next or sends 401.

Express

app.use(function(req, res, [1]) {
  if (!req.user) {
    res.status(401).[2]('Unauthorized');
  } else {
    next();
  }
});

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

Anext

Bsend

Cjson

Dend

Attempts:

3 left

💡 Hint

Common Mistakes

Using end or json instead of send for the response.

The middleware uses next to continue if authenticated, otherwise sends a 401 response with send.

5fill in blank

hard

Fill all three blanks to create middleware that logs method, URL, and calls next.

Express

app.use(function(req, res, [1]) {
  console.log(req.[2] + ' ' + req.[3]);
  next();
});

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

Anext

Bmethod

Curl

Dbody

Attempts:

3 left

💡 Hint

Common Mistakes

Using body instead of url for the request path.

The middleware logs the HTTP method and URL, then calls next() to continue.