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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

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

All Topics

1

Dependency Injection

2

Request Lifecycle

Exception Handling

3

4

Database and ORM

5

Authentication and Authorization