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Welcome to PolyVal

PolyVal is a multilingual and highly customizable validation library that provides developers with a simplified API for data validation. Built on top of Zod, it offers an intuitive approach to validating forms, user input, and data schemas without requiring deep knowledge of complex validation rules.

Installation

Get started by installing PolyVal in your project

Quickstart

Build your first validation in minutes

API Reference

Explore the complete API documentation

Examples

Learn from real-world examples

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Key features

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Simplified API

Define validation schemas using simple JavaScript objects without complex type definitions. PolyVal abstracts away the complexity while maintaining full type safety. 
const schema = {
  email: {
    type: 'string',
    required: true,
    email: true
  },
  age: {
    type: 'number',
    min: 18
  }
};

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Multilingual support

Built-in support for multiple languages with default translations for English and Turkish. Error messages are automatically localized based on your selected language. 
const errors = validate(schema, data, { lang: 'tr' });
// Returns: ["Email: Geçersiz e-posta adresi"]

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Fully customizable error messages

Customize error messages at multiple levels: globally, by type, by field, or for specific validation rules. Complete control over what your users see. 
const errors = validate(schema, data, {
  lang: 'en',
  customMessages: {
    string: {
      email: "That doesn't look like a valid email address."
    },
    fields: {
      username: {
        min: (min) => `Username needs at least ${min} characters`
      }
    }
  }
});

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Custom validation rules

Easily extend PolyVal with your own validation logic. Define custom validators with optional message keys for consistent error handling. 
const schema = {
  username: {
    type: 'string',
    required: true,
    customValidators: [
      {
        validator: (value) => {
          return value.toLowerCase() === 'admin' 
            ? 'Username admin is reserved' 
            : undefined;
        },
        messageKey: 'noAdminUsername'
      }
    ]
  }
};

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TypeScript support

Full TypeScript support with comprehensive type definitions ensures type safety throughout your validation workflow.

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Field comparison

Validate fields against each other with built-in comparison operators. Perfect for password confirmation, date ranges, and related fields. 
const schema = {
  password: {
    type: 'string',
    required: true,
    min: 8
  },
  confirmPassword: {
    type: 'string',
    required: true,
    equals: 'password'
  }
};

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Why PolyVal?

PolyVal bridges the gap between powerful validation libraries like Zod and the need for a simple, intuitive API. It’s designed for developers who want:
  • Quick setup - Start validating data in minutes, not hours
  • Internationalization - Built-in i18n support without extra configuration
  • Flexibility - Customize every aspect of validation and error messages
  • Type safety - Full TypeScript support with intelligent type inference
  • Clean code - Write readable validation schemas that serve as documentation

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Ready to get started?

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