Request body in NestJS - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of the @Body() decorator in NestJS?

The @Body() decorator extracts the data sent in the request body, allowing the controller to access it as a JavaScript object.

intermediate

How do you define a DTO (Data Transfer Object) for validating request body data in NestJS?

A DTO is a TypeScript class that defines the shape and validation rules of the request body using decorators like <code>@IsString()</code> or <code>@IsInt()</code> from the <code>class-validator</code> package.

intermediate

What happens if the request body does not match the DTO validation rules in NestJS?

NestJS automatically returns a 400 Bad Request response with details about the validation errors, preventing the controller method from running.

beginner

How can you access only a specific property from the request body in a NestJS controller?

You can use @Body('propertyName') to extract just that property from the request body directly.

beginner

Why is it important to use DTOs and validation for request bodies in NestJS?

Using DTOs and validation helps keep your app safe by checking data before using it, avoiding errors and security issues from bad or unexpected input.

Which decorator is used to access the entire request body in a NestJS controller?

A @Param()

B @Body()

C @Query()

D @Headers()

The @Body() decorator extracts the whole request body.

What package is commonly used with NestJS to validate request body data?

A express-validator

B yup

C joi

D class-validator

NestJS uses class-validator with DTO classes for validation.

What HTTP status code does NestJS return if request body validation fails?

A 404 Not Found

B 200 OK

C 400 Bad Request

D 500 Internal Server Error

Validation errors cause a 400 Bad Request response.

How do you extract only the 'name' property from the request body in a NestJS controller?

A @Body('name')

B @Param('name')

C @Query('name')

D @Headers('name')

Use @Body('name') to get just the 'name' property.

Why should you use DTOs for request bodies in NestJS?

A To validate and structure incoming data

B To style the response

C To improve database speed

D To handle file uploads

DTOs help validate and organize incoming request data.

Explain how NestJS handles request body data and validation using decorators and DTOs.

Think about how data flows from the client to the controller and how NestJS checks it.

Describe the benefits of extracting specific properties from the request body in a NestJS controller.

Consider why you might want only part of the data instead of the whole object.