ValidationPipe setup in NestJS - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import the ValidationPipe from NestJS.

NestJS

import { [1] } from '@nestjs/common';

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

APipeTransform

BValidationPipe

CController

DInjectable

Attempts:

3 left

💡 Hint

Common Mistakes

Importing unrelated classes like Controller or Injectable.

Confusing ValidationPipe with PipeTransform interface.

The ValidationPipe is imported from @nestjs/common to enable validation features.

2fill in blank

medium

Complete the code to apply ValidationPipe globally in the main.ts file.

NestJS

app.useGlobalPipes(new [1]());

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

AValidationPipe

BLogger

CAuthGuard

DParseIntPipe

Attempts:

3 left

💡 Hint

Common Mistakes

Using pipes unrelated to validation like ParseIntPipe.

Forgetting to instantiate the pipe with new.

Using ValidationPipe globally ensures all incoming requests are validated automatically.

3fill in blank

hard

Fix the error in the ValidationPipe options to enable automatic transformation.

NestJS

app.useGlobalPipes(new ValidationPipe({ transform: [1] }));

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

Afalse

B'true'

Ctrue

DTrue

Attempts:

3 left

💡 Hint

Common Mistakes

Using string 'true' instead of boolean true.

Using capitalized True which is invalid in JavaScript/TypeScript.

The transform option must be a boolean true (without quotes) to enable automatic type conversion.

4fill in blank

hard

Fill both blanks to configure ValidationPipe to whitelist and forbid non-whitelisted properties.

NestJS

app.useGlobalPipes(new ValidationPipe({ whitelist: [1], forbidNonWhitelisted: [2] }));

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

Atrue

Bfalse

Cundefined

Dnull

Attempts:

3 left

💡 Hint

Common Mistakes

Setting these options to false disables the security benefits.

Using undefined or null instead of boolean values.

Setting whitelist and forbidNonWhitelisted to true ensures only allowed properties are accepted and others cause errors.

5fill in blank

hard

Fill all three blanks to create a ValidationPipe with transform, whitelist, and forbidNonWhitelisted enabled.

NestJS

app.useGlobalPipes(new ValidationPipe({ transform: [1], whitelist: [2], forbidNonWhitelisted: [3] }));

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

Afalse

Btrue

Cundefined

Dnull

Attempts:

3 left

💡 Hint

Common Mistakes

Leaving any option false disables part of validation.

Using undefined or null instead of boolean true.

Enabling transform, whitelist, and forbidNonWhitelisted all to true activates full validation and transformation features.

Practice

1. What is the main purpose of using ValidationPipe in a NestJS application?

easy

A. To serve static files like images and CSS

B. To handle database connections automatically

C. To check and clean incoming data to ensure it is safe and correct

D. To manage user authentication and authorization

Solution

1. Step 1: Understand ValidationPipe role

   ValidationPipe is designed to validate and sanitize incoming data in NestJS, ensuring the data meets expected rules.

2. Step 2: Compare with other options

   Other options like database handling, authentication, or serving static files are unrelated to ValidationPipe's purpose.

3. Final Answer:

   To check and clean incoming data to ensure it is safe and correct -> Option C

4. Quick Check:

   ValidationPipe purpose = data validation and cleaning [OK]

Hint: ValidationPipe is all about checking incoming data [OK]

Common Mistakes:

• Confusing ValidationPipe with authentication features
• Thinking ValidationPipe manages database connections
• Assuming ValidationPipe serves static files

2. Which is the correct way to apply ValidationPipe globally in a NestJS app inside main.ts?

easy

A. app.useGlobalPipes(new ValidationPipe())

B. app.usePipes(new ValidationPipe())

C. app.setGlobalPipes(new ValidationPipe())

D. app.applyGlobalPipes(new ValidationPipe())

Solution

1. Step 1: Recall NestJS global pipe method

   The official method to set global pipes is app.useGlobalPipes().

2. Step 2: Check other options

   Methods like usePipes, setGlobalPipes, or applyGlobalPipes do not exist or are incorrect.

3. Final Answer:

   app.useGlobalPipes(new ValidationPipe()) -> Option A

4. Quick Check:

   Global pipe setup = useGlobalPipes() [OK]

Hint: Global pipes use app.useGlobalPipes() [OK]

Common Mistakes:

• Using non-existent methods like setGlobalPipes
• Confusing useGlobalPipes with usePipes
• Missing the 'new' keyword before ValidationPipe

3. Given this main.ts snippet, what will happen when a request sends extra properties not defined in the DTO?

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

medium

A. The request will fail with a validation error

B. Extra properties will be removed from the incoming data

C. Extra properties will be kept without changes

D. The app will crash due to unknown properties

Solution

1. Step 1: Understand whitelist option in ValidationPipe

   Setting whitelist: true removes any properties not defined in the DTO from the incoming data.

2. Step 2: Check behavior on extra properties

   With whitelist true, extra properties are stripped, not causing errors or crashes.

3. Final Answer:

   Extra properties will be removed from the incoming data -> Option B

4. Quick Check:

   whitelist true = remove extra props [OK]

Hint: whitelist true strips unknown properties [OK]

Common Mistakes:

• Thinking whitelist causes validation errors on extra props
• Assuming extra props are kept unchanged
• Believing app crashes on extra properties

4. What is wrong with this main.ts code snippet for setting up ValidationPipe globally?

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

medium

A. Missing 'new' keyword before ValidationPipe

B. The 'transform' option is invalid

C. useGlobalPipes should be called inside a controller

D. ValidationPipe cannot be used globally

Solution

1. Step 1: Check ValidationPipe instantiation

   ValidationPipe is a class and must be instantiated with the new keyword.

2. Step 2: Validate other parts

   The transform option is valid, and useGlobalPipes is correctly used in main.ts.

3. Final Answer:

   Missing 'new' keyword before ValidationPipe -> Option A

4. Quick Check:

   Instantiate ValidationPipe with new [OK]

Hint: Always use 'new' with ValidationPipe class [OK]

Common Mistakes:

• Omitting 'new' keyword when creating ValidationPipe
• Thinking transform option is invalid
• Trying to set global pipes inside controllers

5. You want to automatically convert incoming JSON strings to their expected types in your DTOs. Which ValidationPipe option should you enable globally to achieve this?

hard

A. forbidNonWhitelisted: true

B. whitelist: true

C. disableErrorMessages: true

D. transform: true

Solution

1. Step 1: Understand transform option

   Setting transform: true tells ValidationPipe to convert incoming payloads to the types defined in DTO classes automatically.

2. Step 2: Check other options

   whitelist removes extra properties, forbidNonWhitelisted throws errors on extra props, and disableErrorMessages hides validation errors; none convert types.

3. Final Answer:

   transform: true -> Option D

4. Quick Check:

   transform true = auto type conversion [OK]

Hint: Use transform true to convert types automatically [OK]

Common Mistakes:

• Confusing whitelist with type conversion
• Thinking forbidNonWhitelisted converts types
• Believing disableErrorMessages affects data types