Applying middleware to routes in NestJS - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is middleware in NestJS?

Middleware in NestJS is a function that runs before the route handler. It can modify the request or response, or end the request-response cycle.

beginner

How do you apply middleware to a specific route in NestJS?

You apply middleware by implementing the configure() method in a module and using consumer.apply(MiddlewareClass).forRoutes('route').

beginner

What is the purpose of the next() function in NestJS middleware?

The next() function passes control to the next middleware or route handler. Without calling next(), the request will not continue.

intermediate

Can middleware be applied globally in NestJS? How?

Yes, middleware can be applied globally by using app.use() in the main bootstrap file before starting the app.

intermediate

What types of routes can middleware be applied to in NestJS?

Middleware can be applied to string paths, controller classes, or route objects specifying method and path.

In NestJS, where do you define middleware for specific routes?

A Inside the module's configure() method using consumer.apply()

B Inside the controller's constructor

C In the main.ts file only

D Inside the service class

Middleware for specific routes is defined in the module's configure() method using consumer.apply().

What happens if you forget to call next() in a NestJS middleware?

A The request will automatically continue

B The request will hang and not reach the route handler

C An error is thrown immediately

D The middleware is skipped

Without calling next(), the request does not continue to the next middleware or route handler, causing it to hang.

Which method applies middleware globally in NestJS?

A controller.use()

B consumer.apply()

C app.use()

D module.use()

app.use() applies middleware globally before any route handlers.

Middleware in NestJS can be applied to which of the following?

A String paths, controller classes, route objects

B Only string paths

C Only controller classes

D Only HTTP methods

Middleware can be applied flexibly to string paths, controller classes, or route objects specifying method and path.

What is the main role of middleware in NestJS?

A To replace controllers

B To define routes

C To handle database connections

D To process requests before they reach route handlers

Middleware processes requests before they reach route handlers, often for logging, authentication, or modifying requests.

Explain how to apply middleware to a specific route in NestJS and why you might want to do this.

Think about controlling which routes get extra processing.

Describe the difference between applying middleware globally and applying it to specific routes in NestJS.

Consider the scope of middleware application.