Middleware ordering in NestJS - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to apply middleware globally in NestJS.

NestJS

app.[1](LoggerMiddleware);

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

Ause

Bapply

Cregister

Dadd

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'apply' or 'register' which are not valid methods for middleware application.

Confusing middleware application with module registration.

In NestJS, the use method applies middleware globally.

2fill in blank

medium

Complete the code to apply middleware only to a specific route.

NestJS

consumer
  .apply(AuthMiddleware)
  .forRoutes({ path: '[1]', method: RequestMethod.GET });

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

A/auth

B/users

C/products

D/orders

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing a route unrelated to user authentication.

Using a route that does not exist in the example.

The middleware is applied only to the '/users' GET route.

3fill in blank

hard

Fix the error in the middleware order to ensure LoggerMiddleware runs before AuthMiddleware.

NestJS

consumer
  .apply([1], AuthMiddleware)
  .forRoutes('*');

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

ACorsMiddleware

BAuthMiddleware

CLoggerMiddleware

DCompressionMiddleware

Attempts:

3 left

💡 Hint

Common Mistakes

Placing AuthMiddleware before LoggerMiddleware.

Using unrelated middleware in the order.

Middleware order matters. LoggerMiddleware should be first to log all requests before authentication.

4fill in blank

hard

Fill both blanks to apply two middlewares in correct order for all routes.

NestJS

consumer
  .apply([1], [2])
  .forRoutes('*');

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

ALoggerMiddleware

BAuthMiddleware

CCorsMiddleware

DCompressionMiddleware

Attempts:

3 left

💡 Hint

Common Mistakes

Reversing the middleware order.

Using unrelated middleware.

LoggerMiddleware should run first, then AuthMiddleware, for all routes.

5fill in blank

hard

Fill all three blanks to apply three middlewares in order: Logger, Auth, then Cors for all routes.

NestJS

consumer
  .apply([1], [2], [3])
  .forRoutes('*');

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

AAuthMiddleware

BLoggerMiddleware

CCorsMiddleware

DCompressionMiddleware

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing the order of middleware.

Using CompressionMiddleware instead of CorsMiddleware.

The correct order is LoggerMiddleware first, then AuthMiddleware, then CorsMiddleware for all routes.

Practice

1. In NestJS, why is the order of middleware important when using the apply() method?

easy

A. Because middleware order controls the type of HTTP methods allowed.

B. Because middleware order changes the port number the server listens on.

C. Because middleware order determines the database connection settings.

D. Because middleware runs in the order they are applied, affecting request processing sequence.

Solution

1. Step 1: Understand middleware execution flow

   Middleware functions run in the order they are applied to the request pipeline.

2. Step 2: Recognize impact on request handling

   The order affects how requests are logged, authenticated, or modified before reaching the route handler.

3. Final Answer:

   Because middleware runs in the order they are applied, affecting request processing sequence. -> Option D

4. Quick Check:

   Middleware order = request handling sequence [OK]

Hint: Middleware order controls request flow sequence [OK]

Common Mistakes:

• Thinking middleware order changes server port
• Confusing middleware order with database settings
• Assuming middleware order controls HTTP methods

2. Which of the following is the correct way to apply two middleware functions authMiddleware and loggerMiddleware in order using NestJS apply() method?

easy

A. apply([authMiddleware, loggerMiddleware]).forRoutes('*')

B. apply(loggerMiddleware, authMiddleware).forRoutes('*')

C. apply(authMiddleware, loggerMiddleware).forRoutes('*')

D. apply(loggerMiddleware).apply(authMiddleware).forRoutes('*')

Solution

1. Step 1: Recall correct syntax for multiple middleware

   Use apply(middleware1, middleware2) to apply middleware in order.

2. Step 2: Confirm order matches desired sequence

   To run authMiddleware before loggerMiddleware, list authMiddleware first.

3. Final Answer:

   apply(authMiddleware, loggerMiddleware).forRoutes('*') -> Option C

4. Quick Check:

   apply(mw1, mw2) = correct syntax [OK]

Hint: List middleware in apply() in desired run order [OK]

Common Mistakes:

• Reversing middleware order in apply()
• Using multiple apply() calls incorrectly
• Passing middleware as an array inside apply()

3. Given the following middleware setup in NestJS:

apply(authMiddleware, loggerMiddleware).forRoutes('users')

What will be the order of middleware execution when a request hits the 'users' route?

medium

A. authMiddleware runs first, then loggerMiddleware

B. loggerMiddleware runs first, then authMiddleware

C. Both run simultaneously

D. Only authMiddleware runs

Solution

1. Step 1: Identify middleware order in apply()

   Middleware listed first runs first; here, authMiddleware is first.

2. Step 2: Confirm sequence on route match

   When a request matches 'users', authMiddleware runs before loggerMiddleware.

3. Final Answer:

   authMiddleware runs first, then loggerMiddleware -> Option A

4. Quick Check:

   apply order = execution order [OK]

Hint: First middleware in apply() runs first [OK]

Common Mistakes:

• Assuming middleware run simultaneously
• Thinking last middleware runs first
• Ignoring route matching

4. You wrote this middleware setup in NestJS:

apply(loggerMiddleware, authMiddleware).forRoutes('profile')

But you want authMiddleware to run before loggerMiddleware. What is the fix?

medium

A. Use apply(authMiddleware).apply(loggerMiddleware).forRoutes('profile')

B. Swap the middleware order to apply(authMiddleware, loggerMiddleware).forRoutes('profile')

C. Change forRoutes to forRoutes('auth')

D. No fix needed; order does not matter

Solution

1. Step 1: Identify current middleware order

   Currently, loggerMiddleware runs before authMiddleware.

2. Step 2: Swap middleware order in apply()

   To run authMiddleware first, list it first in apply().

3. Final Answer:

   Swap the middleware order to apply(authMiddleware, loggerMiddleware).forRoutes('profile') -> Option B

4. Quick Check:

   Middleware order in apply() = execution order [OK]

Hint: Swap middleware order in apply() to fix sequence [OK]

Common Mistakes:

• Changing route instead of middleware order
• Using multiple apply() calls incorrectly
• Assuming order does not affect execution

5. You want to log every request before authenticating it and then modify the request body only after authentication in NestJS. Which middleware order should you apply?

hard

A. apply(loggerMiddleware, authMiddleware, modifyBodyMiddleware).forRoutes('*')

B. apply(authMiddleware, loggerMiddleware, modifyBodyMiddleware).forRoutes('*')

C. apply(modifyBodyMiddleware, loggerMiddleware, authMiddleware).forRoutes('*')

D. apply(authMiddleware, modifyBodyMiddleware, loggerMiddleware).forRoutes('*')

Solution

1. Step 1: Determine desired middleware sequence

   Requests should be logged first, then authenticated, then modified.

2. Step 2: Arrange middleware in apply() accordingly

   List loggerMiddleware first, then authMiddleware, then modifyBodyMiddleware.

3. Final Answer:

   apply(loggerMiddleware, authMiddleware, modifyBodyMiddleware).forRoutes('*') -> Option A

4. Quick Check:

   Middleware order = log -> auth -> modify [OK]

Hint: Order middleware as log, auth, then modify [OK]

Common Mistakes:

• Placing modifyBodyMiddleware before authMiddleware
• Logging after authentication
• Incorrect middleware sequence in apply()