Whitelist and transform options in NestJS - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the whitelist option do in NestJS validation?

The whitelist option removes any properties from the input object that are not explicitly defined in the DTO (Data Transfer Object). This helps keep only the allowed data and improves security.

beginner

What is the purpose of the transform option in NestJS validation pipe?

The transform option automatically converts input data types to the types defined in the DTO classes. For example, it can convert a string to a number if the DTO expects a number.

intermediate

How do whitelist and transform options work together in NestJS?

When both options are enabled, NestJS first removes unwanted properties (whitelist) and then converts the remaining data to the correct types (transform). This ensures clean and correctly typed input data.

beginner

How do you enable whitelist and transform options globally in a NestJS app?

You enable them by passing options to the ValidationPipe in the main app file, like this:<br>

app.useGlobalPipes(new ValidationPipe({ whitelist: true, transform: true }));

intermediate

What happens if whitelist is false and extra properties are sent in a request?

If whitelist is false, extra properties not defined in the DTO remain in the input object. This can lead to unexpected data being processed or security risks.

What does setting whitelist: true in NestJS ValidationPipe do?

A Converts input data types automatically

B Allows all properties without filtering

C Disables validation

D Removes properties not in the DTO from the input

The whitelist option removes any properties not defined in the DTO, keeping only allowed data.

What is the effect of transform: true in NestJS ValidationPipe?

A Automatically converts input types to DTO types

B Blocks all invalid requests

C Removes extra properties

D Logs validation errors

Transform converts input data types to match the DTO class types automatically.

How do you enable both whitelist and transform globally in NestJS?

A app.useGlobalPipes(new ValidationPipe({ whitelist: true, transform: true }))

B app.useGlobalPipes(new ValidationPipe({ validate: true }))

C app.useGlobalPipes(new ValidationPipe({ sanitize: true }))

D app.useGlobalPipes(new ValidationPipe({ enable: true }))

You pass both options to ValidationPipe when setting it globally.

If whitelist is false, what happens to extra properties in the request?

A They cause an error

B They remain in the input object

C They are removed

D They are converted to null

Without whitelist, extra properties are not removed and stay in the input.

Why is using whitelist important for security?

A It disables validation

B It speeds up the app

C It prevents unwanted data from being processed

D It encrypts the data

Whitelist removes unexpected properties, reducing risk of malicious data.

Explain how the whitelist and transform options improve data handling in NestJS validation.

Think about filtering and converting input data.

Describe how to set up global validation in NestJS to use whitelist and transform options.

Look at the main app bootstrap file.