How do you write a pipe that validates and parses a date string from a route parameter in NestJS?

Q: How do you write a pipe that validates and parses a date string from a route parameter in NestJS?

@Injectable() export class ParseDatePipe implements PipeTransform { transform(value: string): Date { if (!value) throw new BadRequestException('Date parameter is required'); const date = new Date(value); // new Date() returns Invalid Date for bad strings if (isNaN(date.getTime())) { throw new BadRequestException( `"${value}" is not a valid date. Expected format: YYYY-MM-DD` ); } // Optional business constraint const year = date.getFullYear(); if (year 2100) { throw new BadRequestException('Date must be between 2000 and 2100'); } return date; } } // Usage @Get('reports/:date') getReport(@Param('date', ParseDatePipe) date: Date) { return this.reportService.getByDate(date); } // GET /reports/2024-03-15 -> date is a Date instance new Date('invalid') does not throw — it returns an Invalid Date object; always check isNaN(date.getTime()). Throw BadRequestException with the expected format in the message for good developer experience. Return Date instance so the handler receives a typed value, not a raw string. For timezone-sensitive APIs consider using a library like date-fns parseISO() instead of new Date(). Pair with @IsDate() from class-validator in DTOs for body date fields.

Difficulty: 6/10

Custom Pipes, Date Validation, NestJS Routing

Implement PipeTransform returning a Date, use new Date(value) to parse, check isNaN(date.getTime()) to detect invalid strings, and throw BadRequestException with a clear message including the expected format. Optionally add range constraints for business-specific date validation.

ParseDatePipe with format validation and range check

Date pipe implementation notes:

1
new Date('invalid') does not throw — it returns an Invalid Date object; always check isNaN(date.getTime()).
2
Throw BadRequestException with the expected format in the message for good developer experience.

How do you write a pipe that validates and parses a date string from a route parameter in NestJS?

Difficulty: 6/10

Custom Pipes, Date Validation, NestJS Routing

Implement PipeTransform returning a Date, use new Date(value) to parse, check isNaN(date.getTime()) to detect invalid strings, and throw BadRequestException with a clear message including the expected format. Optionally add range constraints for business-specific date validation.

ParseDatePipe with format validation and range check

Date pipe implementation notes:

1
new Date('invalid') does not throw — it returns an Invalid Date object; always check isNaN(date.getTime()).
2
Throw BadRequestException with the expected format in the message for good developer experience.

How do you write a pipe that validates and parses a date string from a route parameter in NestJS?

Implement PipeTransform returning a Date, use new Date(value) to parse, check isNaN(date.getTime()) to detect invalid strings, and throw BadRequestException with a clear message including the expected format. Optionally add range constraints for business-specific date validation.

How do you write a pipe that validates and parses a date string from a route parameter in NestJS?

Implement PipeTransform returning a Date, use new Date(value) to parse, check isNaN(date.getTime()) to detect invalid strings, and throw BadRequestException with a clear message including the expected format. Optionally add range constraints for business-specific date validation.

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