IsoValid

A lightweight, isomorphic data validation library for TypeScript and JavaScript that works seamlessly in both browser and Node.js environments. IsoValid is designed to provide a unified validation experience across your entire application stack.

Created and maintained by Alok Kaushik | [e-mail]

Why IsoValid?

In modern web applications, data validation is crucial at multiple layers:

• Client-side form validation for immediate user feedback
• API request/response validation for data integrity
• Server-side validation for security

Traditionally, developers had to:

1. Write separate validation logic for frontend and backend
2. Maintain multiple validation libraries
3. Deal with inconsistencies between environments

IsoValid solves these problems by providing:

• 🌐 True Isomorphic Support - The exact same validation code runs in both browser and Node.js
• 🎯 TypeScript-First Design - Built from the ground up with TypeScript for excellent type inference
• 🪶 Minimal Bundle Size - Core validation features without unnecessary bloat
• 🔄 Developer-Friendly API - Intuitive, chainable interface for building schemas
• ⚡ High Performance - Optimized validation with minimal overhead
• 🎨 Extensible Design - Easy to add custom validators and error messages

Installation

npm install isovalid

Architecture

IsoValid is built on a flexible, extensible architecture:

Core Components

1. Base Schema Class

   • Abstract foundation for all schema types
   • Handles common validation logic
   • Manages optional/nullable states

2. Type-Specific Schemas

   • StringSchema: String validation with length, pattern, format checks
   • NumberSchema: Numeric validation with range, integer, sign checks
   • More types coming soon (Boolean, Array, Object)

3. Validation Pipeline

   • Multi-stage validation process
   • Custom validator support
   • Detailed error reporting

API Reference

String Validation

const stringSchema = v.string()
  .min(2)           // Minimum length
  .max(50)          // Maximum length
  .email()          // Email format
  .matches(/regex/) // Custom regex pattern
  .trimmed()        // Auto-trim whitespace
  .setOptional()    // Allow undefined
  .setNullable()    // Allow null
  .custom(value => value.includes('@') ? null : 'Must include @'); // Custom validation

Number Validation

const numberSchema = v.number()
  .min(0)         // Minimum value
  .max(100)       // Maximum value
  .integer()      // Must be an integer
  .positive()     // Must be > 0
  .setOptional()  // Allow undefined
  .setNullable(); // Allow null

Validation Results

All validations return a structured result:

interface ValidationResult {
  valid: boolean;
  errors: Array<{
    path: string[];
    message: string;
  }>;
}

Real-World Examples

1. React Form Validation

import { v } from 'isovalid';
import { useState, FormEvent } from 'react';

const userSchema = {
  username: v.string().min(3).max(20),
  email: v.string().email(),
  age: v.number().integer().min(18)
};

function RegistrationForm() {
  const [formData, setFormData] = useState({
    username: '',
    email: '',
    age: ''
  });
  const [errors, setErrors] = useState<Record<string, string>>({});

  const validateField = (field: keyof typeof userSchema, value: any) => {
    const result = userSchema[field].validate(value);
    return result.valid ? null : result.errors[0].message;
  };

  const handleSubmit = (e: FormEvent) => {
    e.preventDefault();
    const newErrors: Record<string, string> = {};
    
    // Validate all fields
    Object.entries(formData).forEach(([field, value]) => {
      const error = validateField(field as keyof typeof userSchema, value);
      if (error) newErrors[field] = error;
    });

    if (Object.keys(newErrors).length === 0) {
      // Form is valid, submit data
      console.log('Submitting:', formData);
    } else {
      setErrors(newErrors);
    }
  };

  return (
    <form onSubmit={handleSubmit}>
      <div>
        <input
          type="text"
          value={formData.username}
          onChange={e => setFormData(prev => ({ ...prev, username: e.target.value }))}
          placeholder="Username"
        />
        {errors.username && <span className="error">{errors.username}</span>}
      </div>
      {/* Similar fields for email and age */}
      <button type="submit">Register</button>
    </form>
  );
}

2. Express API Validation

import express from 'express';
import { v } from 'isovalid';

const app = express();
app.use(express.json());

const productSchema = {
  name: v.string().min(3).max(100),
  price: v.number().min(0),
  category: v.string().custom(value =>
    ['electronics', 'books', 'clothing'].includes(value)
      ? null
      : 'Invalid category'
  )
};

app.post('/api/products', (req, res) => {
  const errors = Object.entries(productSchema)
    .map(([field, schema]) => ({
      field,
      result: schema.validate(req.body[field])
    }))
    .filter(({ result }) => !result.valid)
    .map(({ field, result }) => ({
      field,
      message: result.errors[0].message
    }));

  if (errors.length > 0) {
    return res.status(400).json({ errors });
  }

  // Process valid product data
  const product = req.body;
  // Save to database, etc.
  res.status(201).json(product);
});

Best Practices

1. Schema Reuse

   • Define schemas once and share between frontend and backend
   • Keep schemas in a shared directory accessible to both environments

2. Type Safety

   • Leverage TypeScript's type inference with IsoValid
   • Define interfaces that match your schemas

3. Performance

   • Create schemas outside request handlers
   • Reuse schema instances when possible

4. Error Handling

   • Always check the valid property before accessing data
   • Provide user-friendly error messages in custom validators

Contributing

We welcome contributions! Please see our Contributing Guide for details.

1. Fork the repository
2. Create your feature branch
3. Write tests for your changes
4. Submit a pull request

Testing

IsoValid uses Jest for testing. Run the test suite:

npm test

Current test coverage: >88%

Roadmap

• [ ] Array schema type
• [ ] Object schema type with nested validation
• [ ] Custom error message templates
• [ ] Async validation support
• [ ] Integration with popular form libraries
• [ ] Schema composition and inheritance

License

MIT © IsoValid

Support

• GitHub Issues: Report bugs and feature requests
• Documentation: Check our Wiki
• Stack Overflow: Tag your questions with isovalid