typescript 43 lines · 7 steps

Validating paginated queries in NestJS

A NestJS controller parses, defaults, and validates query params before delegating a paginated product lookup.

Explained by highlit

NestJS Intermediate pagination validation pipes dependency-injection query-params

1import {
Controller,
Get,
Query,
DefaultValuePipe,
ParseIntPipe,
BadRequestException,
8} from '@nestjs/common';
9import { ProductsService } from './products.service';
10 
11@Controller('products')
12export class ProductsController {
constructor(private readonly productsService: ProductsService) {}
14 
@Get()
async findAll(
  @Query('page', new DefaultValuePipe(1), ParseIntPipe) page: number,
  @Query('limit', new DefaultValuePipe(20), ParseIntPipe) limit: number,
  @Query('minPrice', new DefaultValuePipe(0), ParseIntPipe) minPrice: number,
  @Query('maxPrice', new DefaultValuePipe(Number.MAX_SAFE_INTEGER), ParseIntPipe)
  maxPrice: number,
) {
  if (page < 1) {
    throw new BadRequestException('page must be greater than or equal to 1');
  }
26 
  const boundedLimit = Math.min(Math.max(limit, 1), 100);
28 
  if (minPrice < 0) {
    throw new BadRequestException('minPrice cannot be negative');
  }
32 
  if (maxPrice < minPrice) {
    throw new BadRequestException('maxPrice must be greater than or equal to minPrice');
  }
36 
  return this.productsService.findAll({
    skip: (page - 1) * boundedLimit,
    take: boundedLimit,
    priceRange: { min: minPrice, max: maxPrice },
  });
}
43}

01 / 01

STEP 01

Walkthrough

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Three takeaways

1Pipes give you type-safe query params with sensible defaults before your handler body ever runs.
2Clamp untrusted numeric inputs to safe bounds instead of trusting client-supplied values directly.
3Convert page/limit into skip/take at the boundary so the service layer stays framework-agnostic.

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