Why middleware is Express's core concept - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to add a middleware function that logs every request.

Express

app.use(function(req, res, [1]) { console.log('Request received'); [1](); });

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

Acallback

Bnext

Cdone

Dfinish

Attempts:

3 left

💡 Hint

Common Mistakes

Using a wrong parameter name instead of next causes the middleware chain to break.

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

2fill in blank

medium

Complete the code to create a middleware that handles JSON body parsing.

Express

app.use(express.[1]());

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

Ajson

Brouter

Cstatic

Durlencoded

Attempts:

3 left

💡 Hint

Common Mistakes

Using urlencoded instead of json when expecting JSON data.

The express.json() middleware parses incoming JSON requests.

3fill in blank

hard

Fix the error in the middleware that does not call the next function.

Express

app.use(function(req, res, [1]) { res.send('Hello'); });

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

Anext

Bdone

Ccallback

Dfinish

Attempts:

3 left

💡 Hint

Common Mistakes

Omitting next() causes the request to hang.

Middleware must call next() to pass control unless it ends the response.

4fill in blank

hard

Fill both blanks to create a middleware that checks if user is authenticated and calls next if true.

Express

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

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

Anext

Bdone

Dcallback

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong parameter names or forgetting to call next().

The middleware uses next to continue if the user is authenticated.

5fill in blank

hard

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

Express

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

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

Anext

Bmethod

Curl

Dcallback

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong property names or forgetting to call next().

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