CORS configuration in NestJS - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does CORS stand for and why is it important in web development?

CORS stands for Cross-Origin Resource Sharing. It is important because it controls how resources on a web server can be requested from another domain, helping to keep web applications secure by preventing unauthorized access.

beginner

How do you enable CORS in a NestJS application?

You enable CORS in NestJS by calling the enableCors() method on the app instance, usually in the main.ts file, like app.enableCors(). You can also pass options to customize the behavior.

intermediate

What is the purpose of the origin option in NestJS CORS configuration?

The origin option specifies which domains are allowed to access the server resources. It can be a string, an array of strings, or a function to dynamically allow or deny requests from certain origins.

intermediate

How can you restrict CORS to allow only specific HTTP methods in NestJS?

You can restrict allowed HTTP methods by setting the methods option in the enableCors() configuration, for example: app.enableCors({ methods: ['GET', 'POST'] }).

beginner

What happens if you do not configure CORS in a NestJS API that is accessed from a different domain?

If CORS is not configured, browsers will block requests made from different domains for security reasons. This means your frontend app on another domain won't be able to access your NestJS API.

Which NestJS method is used to enable CORS?

A app.enableCors()

B app.useCors()

C app.setCors()

D app.configureCors()

The correct method to enable CORS in NestJS is app.enableCors().

What does the 'origin' option in CORS configuration control?

A The server port number

B Which HTTP methods are allowed

C Which domains can access the server

D The response format

The 'origin' option controls which domains are allowed to access the server resources.

If you want to allow only GET and POST requests from other domains, which option should you set?

A allowedMethods: ['GET', 'POST']

B corsMethods: ['GET', 'POST']

C httpMethods: ['GET', 'POST']

D methods: ['GET', 'POST']

The correct option is 'methods' to specify allowed HTTP methods in CORS.

What will happen if CORS is not enabled on a NestJS API accessed from a different domain?

A The API will work normally

B The browser will block the request

C The server will crash

D The request will be redirected

Browsers block cross-origin requests if CORS is not enabled for security.

Can the 'origin' option in NestJS CORS configuration accept a function?

A Yes, to dynamically allow or deny origins

B No, only strings are allowed

C No, only arrays are allowed

D Yes, but only for logging purposes

The 'origin' option can be a function to dynamically control allowed origins.

Explain how to enable and customize CORS in a NestJS application.

Think about the main.ts file and the enableCors method.

Describe what problems CORS solves and what happens if it is not configured properly in NestJS.

Consider browser security and cross-origin requests.