Custom validation decorators in NestJS - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import the necessary decorator for custom validation.

NestJS

import { [1] } from 'class-validator';

Drag options to blanks, or click blank then click option'

AIsString

BValidatorConstraint

CValidate

DIsNotEmpty

Attempts:

3 left

💡 Hint

Common Mistakes

Using decorators meant for property validation like IsString instead of ValidatorConstraint.

The ValidatorConstraint decorator is used to define a custom validation constraint class in NestJS.

2fill in blank

medium

Complete the code to implement the ValidatorConstraintInterface.

NestJS

export class CustomTextLengthValidator implements [1] {
  validate(text: string) {
    return text.length > 5;
  }
}

Drag options to blanks, or click blank then click option'

AValidatorConstraintInterface

BValidationArguments

CValidatorConstraint

DValidationOptions

Attempts:

3 left

💡 Hint

Common Mistakes

Using the decorator name instead of the interface name for implementation.

The class must implement ValidatorConstraintInterface to define the validate method for custom validation logic.

3fill in blank

hard

Fix the error in the custom decorator function to apply the validation correctly.

NestJS

export function IsCustomText(validationOptions?: ValidationOptions) {
  return function (object: Object, propertyName: string) {
    [1](CustomTextLengthValidator, {
      message: 'Text is too short',
      ...validationOptions,
    })(object, propertyName);
  };
}

Drag options to blanks, or click blank then click option'

AIsString

BValidatorConstraint

CValidateIf

DValidate

Attempts:

3 left

💡 Hint

Common Mistakes

Using the class decorator ValidatorConstraint instead of the property decorator Validate.

The Validate decorator applies the custom validator class to the property inside the custom decorator function.

4fill in blank

hard

Fill both blanks to complete the custom validator class and decorator usage.

NestJS

import { [1], ValidatorConstraintInterface, ValidationArguments } from 'class-validator';

@ValidatorConstraint({ name: 'customText', [2]: true })
export class CustomTextLengthValidator implements ValidatorConstraintInterface {
  validate(text: string, args: ValidationArguments) {
    return typeof text === 'string' && text.length > 5;
  }
}

Drag options to blanks, or click blank then click option'

AValidatorConstraint

BValidate

Casync

DasyncValidation

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing the async option name or missing the decorator.

The ValidatorConstraint decorator marks the class as a validator. The async option set to true allows asynchronous validation if needed.

5fill in blank

hard

Fill all three blanks to create a custom decorator that uses the validator and accepts validation options.

NestJS

import { Validate, ValidationOptions } from 'class-validator';

export function IsCustomText([1]?: ValidationOptions) {
  return function (object: Object, propertyName: string) {
    [2](CustomTextLengthValidator, {
      message: 'Text must be longer than 5 characters',
      ...[3],
    })(object, propertyName);
  };
}

Drag options to blanks, or click blank then click option'

AvalidationOptions

BValidate

DValidatorConstraint

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong decorator or mismatching parameter names.

The function parameter is named validationOptions. Inside, the Validate decorator is called with the validator class and options spread from validationOptions.