Comparison of zod with class-validator & class-transformer in NestJS

I was confused, or at least curious between zod or class-validator & class-transformer
as a validation library in NestJS.

Main Point

Just go straight to it.

1. Reasons for choosing class-validator & class-transformer

• Is a duo packages that are common & widely used in NestJS
• The writing method is very NestJS because it is decorator-based validation
• clean & seamless integration with its use with class-transformer & ValidationPipe

2. Reasons for choosing Zod

• Framework agnostic
• Very typescript
• For those who prefer functional & schema-based approach
• Performance & lightweight validation is critical

Details

class-validator & class-transformer are the 2 packages most commonly used as validation in NestJS,
yes, apart from the fact that the writing method is the same as NestJS using decorator-based,
also because it is clean & seamless because it can be used with ValidationPipe as DTO.

So the incoming data/payload received by the controller has been validated & changed/transformed according to its definition.
Meanwhile, Zod still needs to manually validate the data/payload received,
Yes, maybe only 1 or a maximum of 3 lines,
but of course the more validation functions are needed, the more manual processes are needed.

Procedure details

The following are detailed procedures (may be subjective) for comparison.

class-validator & class-transformer

1. Installation

npm install class-validator class-transformer

2. Enable Global Validation

// main.ts
....
import { ValidationPipe } from '@nestjs/common';

async function bootstrap() {
....
  // Enable validation globally
  app.useGlobalPipes(new ValidationPipe({
    transform: true, // Automatically transform payloads to DTO instances
    whitelist: true, // Strip unknown properties
    forbidNonWhitelisted: true, // Throw error for unknown properties
  }));
....
}
....

3. Define DTO (Data Transfer Object)

import { IsNotEmpty, IsString, IsInt, Min } from "class-validator";
import { Type, Transform } from "class-transformer";

export class CreateUserDto {
    @Transform(({ value }) => value.trim()) // Trim whitespaces
    @IsNotEmpty({ message: "Nama tidak boleh kosong" })
    @IsString({ message: "Nama harus berupa string" })
    @Min(3, { message: "Minimal panjang nama 3 karakter" })
    name: string;

    @Type(() => Number) // Transform input ke tipe Number
    @IsNotEmpty({ message: "Nama tidak boleh kosong" })
    @IsInt({ message: "Umur harus berupa bilangan bulat" })
    @Min(17, { message: "Minimal umur terdaftar 17 tahun" })
    age: number;
}

It's quite long, but that's how it is decorator-based.

4. Use of validation

import { Body, Controller, Post } from "@nestjs/common";
import { CreateUserDto } from "./create-user.dto";

@Controller("users")
export class UsersController {
    @Post()
    create(@Body() createUserDto: CreateUserDto) {
        // Pada titik ini data/payload createUserdDto
        // sudah tervalidasi & diubah sesuai definisinya
        // developer bisa langsung eksekusi service
        // atau logic yang lain
    }
}

Zod

1. Installation

npm install zod

2. Create Validation Scheme

// user.validaiton.ts
import { z, ZodType } from "zod";

export class UserValidation {
    static readonly CREATE: ZodType = z.object({
        name: z
            .string({ message: "Nama harus berupa string" })
            .nonempty({ message: "Nama tidak boleh kosong" })
            .min(3, "Minimal panjang nama 13 karakter"),
        age: z
            .number({ message: "Umur harus berupa angka" })
            .int({ message: "Umur harus berupa bilangan bulat" })
            .min(17, "Minimal umur terdaftar 17 tahub"),
    });
}

export type TCreateUserPayload = z.infer<typeof UserValidation.CREATE>;

*Personal: I prefer reading this schema than the one above

3. Use of validation

import { Body, Controller, Post } from "@nestjs/common";
import { UserValidation, TCreateUserPayload } from "./user.validation.ts";

@Controller("users")
export class UsersController {
    @Post()
    create(@Body() createUserPayload: TCreateUserPayload) {
        const payload = UserValidation.CREATE.parse(createUserPayload);
        // Pada titik ini data/payload payload
        // sudah tervalidasi & diubah sesuai definisinya
        // developer bisa langsung eksekusi service
        // atau logic yang lain
    }
}

Conclusion

Personally I prefer the way Zod is used.
However, what needs to be underlined is choose according to the team's needs & standards.

https://abdulghofurme.github.io/posts/zod-vs-class-validator-n-class-transformer/

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