TOPIC OVERVIEW

NestJS/Pipes

Validate and transform incoming data before it reaches your controller method.

15 QuestionsIntermediateHigh Priority ~10 min read

Pipes process data before it reaches a controller handler. They can transform values into the type your application expects or validate that incoming data follows specific rules.

NestJS provides built-in pipes such as ParseIntPipe and ValidationPipe, while custom pipes can handle application-specific requirements. Pipes are particularly useful for keeping validation and transformation logic out of your controllers.

What you'll walk away knowing

What pipes do in the NestJS request lifecycle

How built-in parsing pipes work

How ValidationPipe validates DTOs

How to create custom pipes

1How do you make a custom pipe configurable by accepting constructor options in NestJS?Intermediate 2How do you validate arrays and conditional fields with class-validator in NestJS?Intermediate 3What is the @ValidateNested() decorator and when must you pair it with @Type()?Intermediate 4What is the difference between a transformation pipe and a validation pipe in NestJS?Intermediate 5How do you write a custom pipe for parsing and validating a MongoDB ObjectId param in NestJS?Intermediate 6How do you write a pipe that uses metatype to skip validation for primitive types the same way ValidationPipe does?Intermediate 7What are the two ways to register a global pipe in NestJS and what is the difference?Intermediate 8How does ValidationPipe work with class-validator and class-transformer in NestJS?Intermediate 9How do you write a custom class-validator decorator in NestJS?Intermediate 10How do you customise the error response format produced by ValidationPipe in NestJS?Intermediate 11How do you write an async custom validator that checks uniqueness against a database in NestJS?Intermediate 12What interface must a custom pipe implement and what does the transform() method receive?Beginner 13What are all the significant ValidationPipe options and what does each do in NestJS?Intermediate 14How do you write a pipe that validates and parses a date string from a route parameter in NestJS?Intermediate 15What is a pipe in NestJS and what are its two primary uses?Intermediate 16What is class-transformer and how does it complement class-validator in NestJS?Intermediate 17What does the @Transform() decorator do in class-transformer and when should you use it?Intermediate 18How does @Type() interact with discriminated unions and polymorphic DTOs in class-transformer?Advanced 19What is class-validator and how does it integrate with NestJS ValidationPipe?Intermediate 20How do you unit test a custom pipe in NestJS?Intermediate 21What does @Exclude() and @Expose() do and how do you use them to strip sensitive fields from responses?Intermediate 22What are all the built-in pipes NestJS ships with?Intermediate 23What is the excludeExtraneousValues option in class-transformer and how does it differ from whitelist in ValidationPipe?Intermediate 24How do you handle file upload validation with ParseFilePipe and custom file validators in NestJS?Intermediate 25How do you write a custom pipe that sanitizes a string input (trim and lowercase) in NestJS?Intermediate 26How do you pass options to a built-in pipe like ParseIntPipe or ParseUUIDPipe in NestJS?Intermediate 27What is the difference between applying a pipe at the param level vs handler level vs globally in NestJS?Intermediate 28Can a pipe be asynchronous in NestJS and how do you implement one?Intermediate 29How do you use validation groups with class-validator to apply different rules for create vs update operations in NestJS?Intermediate

All Topics

1

Dependency Injection

2

Request Lifecycle

Exception Handling

3

4

Database and ORM

5

Authentication and Authorization

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