🚀 Fast Form Validator (FFV)

A lightweight, chainable JavaScript form validation library with zero dependencies. Simple API, powerful validation, works everywhere.

✨ Features

🔗 Chainable API - Fluent, readable syntax
🎯 Zero Dependencies - Pure JavaScript, no bloat
📦 Tiny Bundle - Less than 5KB minified + gzipped
🎨 Customizable - Create your own validation strategies
🔧 Framework Agnostic - Works with vanilla JS, React, Vue, etc.
💪 TypeScript Support - Full type definitions included
♿ Accessible - WCAG compliant error messaging
🌐 Browser Support - IE11+ and all modern browsers

📦 Installation

NPM

npm install fast-form-validator

CDN

<script src="https://unpkg.com/fast-form-validator@latest/UMD/ffv.min.js"></script>

🚀 Quick Start

HTML

<form id="signup-form">
  <input type="email" id="email" />
  <input type="password" id="password" />
  <input type="date" id="dob" />
  <button type="submit" id="submit-btn">Sign Up</button>
  <div id="error-messages"></div>
</form>

JavaScript (Browser)

FFV.onEmail('email')
   .onPassword('password', 8, 20)
   .onDateOfBirth('dob', 18)
   .displayErrorsHere('error-messages')
   .onSuccess.removeFeedback()
   .onSubmitButton('submit-btn', handleSubmit)
   .validate();

function handleSubmit() {
  console.log('Form is valid!');
  // Submit your form data
}

JavaScript (Module)

import { FastFormValidator } from 'fast-form-validator';

const validator = new FastFormValidator();

validator
  .onEmail('email')
  .onPassword('password', 8, 20)
  .displayErrorsHere('error-messages')
  .validate();

📚 API Reference

Built-in Validators

`onEmail(id: string)`

Validates email format.

FFV.onEmail('email-field');

`onPassword(id: string, minLength?: number, maxLength?: number)`

Validates password with complexity requirements (uppercase, lowercase, digit).

FFV.onPassword('password-field', 8, 20);
// Defaults: min=6, max=15

`onDateOfBirth(id: string, minAge?: number)`

Validates age requirement.

FFV.onDateOfBirth('dob-field', 18);
// Default: minAge=18

Custom Validation

`setStrategyFor(id: string, validationFn: Function, ...args: any[])`

Create custom validation logic.

function validateUsername() {
  const value = this.usernameValue;
  
  if (!value) {
    this.usernameError = 'Username is required';
  }
  
  if (value.length < 3) {
    this.usernameError = 'Username must be at least 3 characters';
  }
  
  if (!/^[a-zA-Z0-9_]+$/.test(value)) {
    this.usernameError = 'Username can only contain letters, numbers, and underscores';
  }
}

FFV.setStrategyFor('username', validateUsername);

With Parameters:

function validateMinLength(id, minLen) {
  const value = this[`${id}Value`];
  
  if (value.length < minLen) {
    this[`${id}Error`] = `Must be at least ${minLen} characters`;
  }
}

FFV.setStrategyFor('bio', validateMinLength, 'bio', 50);

Display & Feedback

`displayErrorsHere(id: string)`

Specify where to show validation errors.

FFV.displayErrorsHere('error-container');

`onSuccess.hideFeedback()`

Hide errors using visibility: hidden when valid.

FFV.onSuccess.hideFeedback();

`onSuccess.removeFeedback()`

Hide errors using display: none when valid.

FFV.onSuccess.removeFeedback();

`onSuccess.addClass(className: string)`

Add a CSS class when validation succeeds.

FFV.onSuccess.addClass('valid-form');

`onSuccess.removeClass(className: string)`

Remove a CSS class when validation succeeds.

FFV.onSuccess.removeClass('has-errors');

Form Submission

`onSubmitButton(id: string, callback: Function)`

Handle form submission after successful validation.

FFV.onSubmitButton('submit-btn', () => {
  // Only called when form is valid
  submitFormData();
});

Validation Control

`validate()`

Start validation and attach event listeners.

const isValid = FFV.validate();
console.log(isValid); // true or false

🎨 Advanced Examples

Multiple Forms on One Page

// Form 1
const loginForm = new FastFormValidator();
loginForm
  .onEmail('login-email')
  .onPassword('login-password')
  .displayErrorsHere('login-errors')
  .validate();

// Form 2
const signupForm = new FastFormValidator();
signupForm
  .onEmail('signup-email')
  .onPassword('signup-password', 10, 30)
  .displayErrorsHere('signup-errors')
  .validate();

Conditional Validation

function validateConfirmPassword() {
  const password = this.passwordValue;
  const confirm = this.confirmPasswordValue;
  
  if (password !== confirm) {
    this.confirmPasswordError = 'Passwords do not match';
  }
}

FFV.onPassword('password')
   .setStrategyFor('confirmPassword', validateConfirmPassword)
   .validate();

Async Validation

function validateUsername() {
  const username = this.usernameValue;
  
  if (!username) {
    this.usernameError = 'Username required';
    return;
  }
  
  // Note: FFV validates synchronously, so handle async externally
  // or use debouncing in your strategy
  
  // Example with debouncing
  clearTimeout(this.usernameTimeout);
  this.usernameTimeout = setTimeout(async () => {
    const available = await checkUsernameAvailability(username);
    if (!available) {
      this.usernameError = 'Username already taken';
      this.validate(); // Re-trigger validation
    }
  }, 500);
}

React Integration

import { useEffect, useRef } from 'react';
import { FastFormValidator } from 'fast-form-validator';

function SignupForm() {
  const validatorRef = useRef(null);
  
  useEffect(() => {
    validatorRef.current = new FastFormValidator();
    
    validatorRef.current
      .onEmail('email')
      .onPassword('password', 8, 20)
      .displayErrorsHere('errors')
      .onSubmitButton('submit', handleSubmit)
      .validate();
    
    return () => {
      validatorRef.current.destroy();
    };
  }, []);
  
  const handleSubmit = () => {
    console.log('Form submitted!');
  };
  
  return (
    <form>
      <input type="email" id="email" />
      <input type="password" id="password" />
      <button type="submit" id="submit">Sign Up</button>
      <div id="errors"></div>
    </form>
  );
}

Custom Error Styling

FFV.onEmail('email')
   .displayErrorsHere('errors')
   .onSuccess.removeClass('error-visible')
   .validate();

#errors {
  padding: 1rem;
  border-radius: 4px;
  margin-top: 1rem;
}

#errors.error-visible {
  background: #fee;
  border: 1px solid #c33;
  color: #c33;
}

#errors:not(.error-visible) {
  display: none;
}

🔧 Migration Guide

From v1.x to v2.x

Breaking Changes:

Multiple Instances: If you need multiple forms, use new FastFormValidator() instead of the global FFV

// Old (v1.x) - only one form per page
FFV.onEmail('email').validate();

// New (v2.x) - multiple forms supported
const form1 = new FastFormValidator();
form1.onEmail('email1').validate();

const form2 = new FastFormValidator();
form2.onEmail('email2').validate();

// Or keep using global FFV for single form
FFV.onEmail('email').validate();

Error Handling: Missing DOM elements now throw errors instead of console warnings

// Add error handling if elements might not exist
try {
  FFV.displayErrorsHere('errors').validate();
} catch (error) {
  console.error('Validation setup failed:', error);
}

🎮 Live Demo

See Fast Form Validator in action: CodePen Demo

🤝 Contributing

Contributions are welcome! Please read our Contributing Guide first.

Fork the repository
Create your feature branch (git checkout -b feature/amazing-feature)
Commit your changes (git commit -m 'Add amazing feature')
Push to the branch (git push origin feature/amazing-feature)
Open a Pull Request

Development

# Install dependencies
npm install

# Run tests
npm test

# Run tests in watch mode
npm run test:watch

# Build for production
npm run build

# Run linter
npm run lint

📝 License

🙏 Acknowledgments

Inspired by the Strategy Pattern and fluent interfaces
Built with ❤️ for the JavaScript community

📞 Support

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