How do you extract and type query parameters in NestJS including optional ones with defaults?

Q: How do you extract and type query parameters in NestJS including optional ones with defaults?

// Single query param — string by default @Get() findAll(@Query('search') search: string) {} // DefaultValuePipe for fallback + ParseIntPipe for type @Get() findAll( @Query('page', new DefaultValuePipe(1), ParseIntPipe) page: number, @Query('limit', new DefaultValuePipe(20), ParseIntPipe) limit: number, ) {} // GET /users -> page=1, limit=20 // GET /users?page=3 -> page=3, limit=20 // DTO approach — cleanest for many optional params export class PaginationQueryDto { @IsOptional() @IsInt() @Min(1) @Type(() => Number) page?: number = 1; @IsOptional() @IsInt() @Min(1) @Max(100) @Type(() => Number) limit?: number = 20; @IsOptional() @IsString() search?: string; } @Get() findAll(@Query() query: PaginationQueryDto) { const { page, limit, search } = query; } Query string values are always strings — use @Type(() => Number) or ParseIntPipe for numeric conversion. DefaultValuePipe should come before ParseIntPipe in the pipe chain so the fallback is also converted. For endpoints with 3+ query params use a DTO class with @Query() — it scales much better. ValidationPipe with transform: true is required for @Type() decorators on query DTOs to work. Mark every query DTO field as @IsOptional() — missing query params should never throw 400.

Difficulty: 5/10

Query DTOs, ValidationPipe, Default values

Use @Query('key') for single params, DefaultValuePipe for fallback values, and ParseIntPipe for type conversion. For endpoints with many optional query params, declare a DTO class and use @Query() with no argument combined with a global ValidationPipe with transform: true.

Query param extraction with types and defaults

Query param best practices:

1
Query string values are always strings — use @Type(() => Number) or ParseIntPipe for numeric conversion.
2
DefaultValuePipe should come before ParseIntPipe in the pipe chain so the fallback is also converted.

How do you extract and type query parameters in NestJS including optional ones with defaults?

Difficulty: 5/10

Query DTOs, ValidationPipe, Default values

Use @Query('key') for single params, DefaultValuePipe for fallback values, and ParseIntPipe for type conversion. For endpoints with many optional query params, declare a DTO class and use @Query() with no argument combined with a global ValidationPipe with transform: true.

Query param extraction with types and defaults

Query param best practices:

1
Query string values are always strings — use @Type(() => Number) or ParseIntPipe for numeric conversion.
2
DefaultValuePipe should come before ParseIntPipe in the pipe chain so the fallback is also converted.

How do you extract and type query parameters in NestJS including optional ones with defaults?

Use @Query('key') for single params, DefaultValuePipe for fallback values, and ParseIntPipe for type conversion. For endpoints with many optional query params, declare a DTO class and use @Query() with no argument combined with a global ValidationPipe with transform: true.

How do you extract and type query parameters in NestJS including optional ones with defaults?

Use @Query('key') for single params, DefaultValuePipe for fallback values, and ParseIntPipe for type conversion. For endpoints with many optional query params, declare a DTO class and use @Query() with no argument combined with a global ValidationPipe with transform: true.

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