Vest is a lightweight JavaScript validation framework designed for complex forms and data structures. It offers a declarative approach to validation, allowing developers to define validation rules in a clear and organized manner. Vest supports asynchronous validations and provides a suite of built-in validation functions.

Pros

• Flexible and extensible, allowing custom validation rules
• Supports both synchronous and asynchronous validations
• Provides detailed validation results, including field-specific errors
• Lightweight and has no dependencies

Cons

• Learning curve for developers new to declarative validation approaches
• Limited built-in localization support
• May require additional setup for complex validation scenarios
• Documentation could be more comprehensive for advanced use cases

Code Examples

1. Basic validation suite:

import { create, test, enforce } from 'vest';

const suite = create((data = {}) => {
  test('username', 'Username is required', () => {
    enforce(data.username).isNotEmpty();
  });

  test('email', 'Email must be valid', () => {
    enforce(data.email).isEmail();
  });
});

2. Asynchronous validation:

import { create, test, enforce } from 'vest';

const suite = create((data = {}) => {
  test('username', 'Username must be unique', async () => {
    const isUnique = await checkUsernameUniqueness(data.username);
    enforce(isUnique).isTruthy();
  });
});

3. Custom validation function:

import { create, test, enforce } from 'vest';

enforce.extend({ isValidPostalCode: (value) => /^\d{5}(-\d{4})?$/.test(value) });

const suite = create((data = {}) => {
  test('postalCode', 'Invalid postal code', () => {
    enforce(data.postalCode).isValidPostalCode();
  });
});

Getting Started

To use Vest in your project, first install it via npm:

npm install vest

Then, create a validation suite:

import { create, test, enforce } from 'vest';

const validationSuite = create((data = {}) => {
  test('name', 'Name is required', () => {
    enforce(data.name).isNotEmpty();
  });

  test('email', 'Email must be valid', () => {
    enforce(data.email).isEmail();
  });
});

// Run the validation
const result = validationSuite({ name: 'John', email: 'john@example.com' });
console.log(result.hasErrors()); // false