Middleware ordering matters in Node.js - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

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

Node.js

app.use([1]);

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

AloggerMiddleware

Bexpress.json()

CerrorHandler

Drouter

Attempts:

3 left

💡 Hint

Common Mistakes

Using errorHandler instead of loggerMiddleware

Adding router before loggerMiddleware

Using express.json() which parses JSON, not logs

The loggerMiddleware logs every request. It should be added with app.use() to run on all requests.

2fill in blank

medium

Complete the code to parse JSON bodies in requests.

Node.js

app.use([1]);

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

AloggerMiddleware

BerrorHandler

Cexpress.json()

Drouter

Attempts:

3 left

💡 Hint

Common Mistakes

Using loggerMiddleware instead of express.json()

Adding errorHandler before routes

Not adding JSON parser middleware at all

express.json() is middleware that parses JSON request bodies. It should be added before routes that need to read JSON data.

3fill in blank

hard

Fix the error in middleware order to ensure errorHandler catches errors.

Node.js

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

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

AloggerMiddleware

BerrorHandler

Cexpress.json()

Dcors()

Attempts:

3 left

💡 Hint

Common Mistakes

Adding errorHandler before router

Using loggerMiddleware as error handler

Not adding errorHandler at all

Error handling middleware must be added after all route handlers to catch errors properly.

4fill in blank

hard

Fill both blanks to add JSON parsing and routing middleware in correct order.

Node.js

app.use([1]);
app.use([2]);

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

Aexpress.json()

Brouter

CerrorHandler

DloggerMiddleware

Attempts:

3 left

💡 Hint

Common Mistakes

Reversing the order of JSON parser and router

Adding errorHandler before router

Adding loggerMiddleware after router

JSON parsing middleware must come before routing middleware so routes can access parsed data.

5fill in blank

hard

Fill all three blanks to add logging, JSON parsing, and error handling middleware in correct order.

Node.js

app.use([1]);
app.use([2]);
app.use([3]);

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

AloggerMiddleware

Bexpress.json()

CerrorHandler

Drouter

Attempts:

3 left

💡 Hint

Common Mistakes

Placing errorHandler before logger or JSON parser

Skipping loggerMiddleware

Adding router instead of errorHandler last

Logging middleware should run first, then JSON parsing, then error handling last.