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 {
2 Controller,
3 Get,
4 Query,
5 DefaultValuePipe,
6 ParseIntPipe,
7 BadRequestException,
8} from '@nestjs/common';
9import { ProductsService } from './products.service';
10 
11@Controller('products')
12export class ProductsController {
13 constructor(private readonly productsService: ProductsService) {}
14 
15 @Get()
16 async findAll(
17 @Query('page', new DefaultValuePipe(1), ParseIntPipe) page: number,
18 @Query('limit', new DefaultValuePipe(20), ParseIntPipe) limit: number,
19 @Query('minPrice', new DefaultValuePipe(0), ParseIntPipe) minPrice: number,
20 @Query('maxPrice', new DefaultValuePipe(Number.MAX_SAFE_INTEGER), ParseIntPipe)
21 maxPrice: number,
22 ) {
23 if (page < 1) {
24 throw new BadRequestException('page must be greater than or equal to 1');
25 }
26 
27 const boundedLimit = Math.min(Math.max(limit, 1), 100);
28 
29 if (minPrice < 0) {
30 throw new BadRequestException('minPrice cannot be negative');
31 }
32 
33 if (maxPrice < minPrice) {
34 throw new BadRequestException('maxPrice must be greater than or equal to minPrice');
35 }
36 
37 return this.productsService.findAll({
38 skip: (page - 1) * boundedLimit,
39 take: boundedLimit,
40 priceRange: { min: minPrice, max: maxPrice },
41 });
42 }
43}
01 / 01
STEP 01

Walkthrough

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

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