Custom Data Validator

A flexible and lightweight data validation library for Node.js applications.

Features
Installation
Quick Start
Usage
Examples
- Basic Usage
- Custom Validation Function
API Reference
- Validator Class
- Built-in Validation Methods
Testing
Contributing
License
Acknowledgments

Features

Simple and Intuitive API: Define validation rules with minimal code.
Built-in Validation Rules: Common validations like required fields, data types, length constraints, and pattern matching. -Auto-Trim and Case Normalization: Automatically trim whitespace and normalize case for string inputs.
Custom Validation Support: Easily add your own validation functions.
Detailed Error Messages: Provides clear and customizable error messages.
Chainable Rules: Apply multiple validation rules to a single field.
Field-wise Validation: Validates each field independently for precise error reporting.
Advanced Password Validation: Validates that a password includes minimum and maximum length, uppercase and lowercase letters, special characters, numbers, no sequential or repeated characters, and disallows common passwords and spaces.

Installation

Install the package via npm:

npm install custom-data-validator

Quick Start

Here's a simple example to get you started:

const { Validator } = require(‘custom-data-validator’);

const rules = {
username: [‘required’, ‘string’, ‘minLength:3’, ‘maxLength:15’],
email: [‘required’, ‘string’, ‘validateEmail’],
age: [‘number’],
isAdmin: [‘boolean’],
};

const data = {
username: ’ john_doe ’,
email: ’ John.Doe@Example.com ’,
age: 28,
isAdmin: false,
};

const validator = new Validator(rules);
const isValid = validator.validate(data);

if (isValid) {
console.log(‘Validation passed!’);
} else {
console.log(‘Validation errors:’, validator.getErrors());
}

Usage

Defining Validation Rules

Validation rules are defined as an object where each key corresponds to a field in your data, and the value is an array of validation rules to apply to that field.

const rules = { fieldName: ['rule1', 'rule2:param', 'customRule'], };

-fieldName: The name of the field in your data object. rule1, rule2 : Validation rules to apply to the field.

Available Validation Rules

required: The field must be present and not empty.
string: The field must be a string.
number: The field must be a number.
boolean: The field must be a boolean.
array: The field must be an array.
object: The field must be an object.
minLength : The string or array must be at least X characters/items long.
maxLength : The string or array must be no more than X characters/items long.
regex : The string must match the provided regular expression pattern. validateEmail: The field must be a valid email address.
validatePassword: Ensures that the password meets complex security requirements, including:
- Minimum and maximum length
- At least one uppercase letter, one lowercase letter, one special character, and one number
- No sequential or repeated characters
- Disallows common passwords and spaces

Auto-Trim and Case Normalization

This feature ensures that user inputs are automatically trimmed of extra spaces and, optionally, case-normalized (e.g., making emails all lowercase). It significantly improves data consistency and reduces common user input issues, especially in forms.

Available Validation Rules

Why It's Impactful:

Improves Data Quality: Prevents common errors like leading/trailing spaces in usernames, emails, or other fields that could cause validation issues.
User-Friendly: Avoids user frustration with inputs being rejected for small formatting issues.
Simple to Implement: It only takes a few lines of code to add trimming and normalization before validation begins.

Improves Data Quality: Prevents common errors like leading/trailing spaces in usernames, emails, or other fields that could cause validation issues. User-Friendly: Avoids user frustration with inputs being rejected for small formatting issues. Simple to Implement: It only takes a few lines of code to add trimming and normalization before validation begins.

**Auto-Trim: Remove leading and trailing spaces from all string inputs. **Email Normalization**: Automatically convert email inputs to lowercase to avoid case-sensitivity issues.

Usage:

By default, you should manually trim and normalize your inputs before validation to ensure data consistency.

const { Validator, normalizeEmail } = require('custom-data-validator');

const data = {
username: ' JohnDoe ',
email: ' John.Doe@Example.com ',
};

// Auto-trim string inputs
data.username = data.username.trim();

// Normalize email before validation
data.email = normalizeEmail(data.email);

const rules = {
username: ['required', 'string', 'minLength:3'],
email: ['required', 'validateEmail'],
};

const validator = new Validator(rules);
const isValid = validator.validate(data);

Custom Validators

You can add your own custom validation functions to extend the validator’s capabilities.

validator.addCustomValidator('isEven', (field, value, param, validatorInstance) => {
if (value % 2 !== 0) {
validatorInstance.addError(field, `${field} must be an even number.`);
}
});

const rules = {
code: ['required', 'number', 'isEven'],
};

const data = { code: 3 };

validator.rules = rules;
const isValid = validator.validate(data);

if (!isValid) {
console.log(validator.getErrors());
}

Error Handling

The validator collects errors for each field during validation. Use validator.getErrors() to retrieve the errors.

if (!isValid) {
const errors = validator.getErrors();
console.log(errors);
// Output:
// {
// code: ['code must be an even number.']
// }
}

Examples

Basic Usage

Password Validation Example

const rules = {
  password: ["validatePassword"]
};

const data = {
  password: "Strong@12345"
};

const validator = new Validator(rules);
const isValid = validator.validate(data);

if (!isValid) {
  console.log("Errors:", validator.getErrors());
} else {
  console.log("Password is valid!");
}

const { Validator, normalizeEmail } = require('custom-data-validator');

const rules = {
name: ['required', 'string', 'minLength:2'],
email: ['required', 'validateEmail'],
password: ['required', 'string', 'minLength:6'],
age: ['number'],
termsAccepted: ['required', 'boolean'],
};

const data = {
name: ' Alice ',
email: ' alice@example.com ',
password: 'secret123',
age: 30,
termsAccepted: true,
};

// Auto-trim and normalize inputs
data.name = data.name.trim();
data.email = normalizeEmail(data.email);

const validator = new Validator(rules);
const isValid = validator.validate(data);

if (isValid) {
console.log('All data is valid!');
} else {
console.error('Validation errors:', validator.getErrors());
}

Custom Validation Function

## Custom Validation Function

# Custom Validation Function



// Custom validator to check if a number is positive
validator.addCustomValidator('isPositive', (field, value, param, validatorInstance) => {
if (value <= 0) {
validatorInstance.addError(field, `${field} must be a positive number.`);
}
});

const rules = {
amount: ['required', 'number', 'isPositive'],
};

const data = { amount: -5 };

validator.rules = rules;
const isValid = validator.validate(data);

if (!isValid) {
console.log(validator.getErrors());
// Output:
// {
// amount: ['amount must be a positive number.']
// }
}

API Reference

Validator Class

The Validator class is the core of the Custom Data Validator package. It allows you to define validation rules for your data and provides methods to perform validations and handle errors.

Constructor

# API Reference

# Validator Class

# Constructor


const validator = new Validator(rules);

rules: An object defining validation rules for each field in your data. Each rule is an array of validation methods or custom validation functions.

const rules = {
  username: ['required', 'string', 'minLength:3', 'maxLength:15'],
  email: ['required', 'validateEmail'],
};
const validator = new Validator(rules);

Methods

1. validate(data) This method runs the validation on the provided data object based on the defined rules.

data: An object where the keys are field names and values are the data to be validated. Returns: true if validation passes, false otherwise.

const data = { username: 'JohnDoe', email: 'john@example.com' };
const isValid = validator.validate(data);

2. getErrors() Retrieves the error messages collected during validation. The returned object contains field names as keys and arrays of error messages as values.

Returns: An object with field names as keys and error messages as values.

Example:

if (!isValid) {
  const errors = validator.getErrors();
  console.log(errors);
  // Output: { username: ['username must be at least 3 characters'], email: ['email is not valid'] }
}```

**3. addCustomValidator(name, validationFunction) **

Adds a custom validation function to extend the built-in validators.

**name**: The name of the custom rule.
**validationFunction**: A function with the signature (field, value, param, validatorInstance) that performs the validation.
- **validatePassword(field, value, minLength = 8)**: Validates that a password contains at least one uppercase letter, one special character, one number, and meets a minimum length requirement (default is 8 characters).

Example:

```javascript
validator.addCustomValidator('isEven', (field, value, param, validatorInstance) => {
  if (value % 2 !== 0) {
    validatorInstance.addError(field, `${field} must be an even number.`);
  }
});

const rules = { number: ['required', 'isEven'] };

4.addError(field, message)

Manually adds an error message for a specific field. Useful for custom validators.

field: The field name. message: The error message to add.

Example:

validator.addError('username', 'Username cannot contain special characters.');

5. resetErrors()

Clears all errors from the validator. Useful if you need to validate multiple sets of data.

Example:

validator.resetErrors();

Built-in Validation Methods

required(field, value): Ensures that the field is present and not empty.
string(field, value): Validates that the value is a string.
number(field, value): Ensures the value is a number.
boolean(field, value): Validates that the value is a boolean.
array(field, value): Ensures the value is an array.
object(field, value): Validates that the value is an object.
minLength(field, value, length): Ensures the string or array is at least length characters/items long.
maxLength(field, value, length): Ensures the string or array is no more than length characters/items long.
regex(field, value, pattern): Ensures the string matches the provided regular expression pattern.
validateEmail(field, value): Validates that the value is a correctly formatted email address.
validatePassword(field, value, options = {}): Validates the strength and security of a password. Default criteria include:
- Minimum length: 8 characters (customizable via options.minLength)
- Maximum length: 20 characters (customizable via options.maxLength)
- Character Requirements:
  - At least one uppercase letter
  - At least one lowercase letter
  - At least one special character (e.g., !@#$%^&*())
  - At least one number
- No Sequential Characters: Disallows sequences like "1234" or "abcd".
- No Repeated Characters: Prevents three or more repeated characters in a row.
- No Common Passwords: Disallows weak passwords like "password123".
- No Spaces: Passwords should not contain spaces.
- Mixed Character Types: Passwords must contain letters, numbers, and special characters for security. Each of these methods is automatically applied when a rule is defined in the validation rules object.

Custom Validation Functions

You can define custom validation functions if you need to implement specific logic that is not covered by the built-in validators.

Example of a custom validator:

validator.addCustomValidator('isOdd', (field, value, param, validatorInstance) => {
  if (value % 2 === 0) {
    validatorInstance.addError(field, `${field} must be an odd number.`);
  }
});

const rules = {
  number: ['required', 'number', 'isOdd'],
};

const data = { number: 4 };

const isValid = validator.validate(data);
if (!isValid) {
  console.log(validator.getErrors());
  // Output: { number: ['number must be an odd number.'] }
}

Error Handling

Errors are automatically collected during validation and can be accessed using the getErrors() method.

Example of handling validation errors:

const isValid = validator.validate(data);

if (!isValid) {
  const errors = validator.getErrors();
  console.error('Validation Errors:', errors);
}

Errors are stored as an object where the keys are the field names, and the values are arrays of error messages. This allows for detailed and precise error reporting.

Methods

validate(data): Validates the provided data against the rules.
data: The data object to validate.
Returns: true if validation passes, false otherwise.
getErrors(): Retrieves the errors collected during validation.
Returns: An object where keys are field names and values are arrays of error messages.
addCustomValidator(name, function): Adds a custom validation function.
Name: The name of the custom rule.
function: The validation function with the signature (field, value, param, validatorInstance).

Built-in Validation Methods

required(field, value)
string(field, value)
number(field, value)
boolean(field, value)
array(field, value)
object(field, value)
minLength(field, value, length)
maxLength(field, value, length)
regex(field, value, pattern)
validateEmail(field, value)

required(field, value) string(field, value) number(field, value) boolean(field, value) array(field, value) object(field, value) minLength(field, value, length) maxLength(field, value, length) regex(field, value, pattern) validateEmail(field, value)

Each method performs a specific validation and adds an error message to the validator instance if the validation fails.

Testing

The package uses Jest for testing. To run the tests, use: The package includes tests for password validation to ensure strong passwords are enforced. You can run the tests by executing:

npm test

## License

This project is licensed under the MIT License - see the LICENSE file for details.
MIT License

# Testing

The package uses Jest for testing. To run the tests, use:
npm test

# Contributing

Contributions are welcome! Please follow these steps:

	1.	Fork the repository.
	2.	Create a new branch:
git checkout -b feature/your-feature-name
  3.	Make your changes and commit them:
git commit -m 'Add some feature'
 	4.	Push to the branch:
git push origin feature/your-feature-name

5.	Open a pull request.

Please ensure your code follows the project’s coding standards and includes appropriate tests.

# Coding Guidelines

	•	Write clear, concise, and self-documenting code.
	•	Use consistent naming conventions.
	•	Include comments where necessary.
	•	Write unit tests for new features or bug fixes.

# Reporting Issues

If you encounter any issues or bugs, please open an issue on GitHub with detailed information.

# License

This project is licensed under the MIT License - see the LICENSE file for details.
MIT License

Permission is hereby granted, free of charge, to any person obtaining a copy...

# Acknowledgments

    •	Inspired by the need for a simple yet powerful data validation solution in Node.js.
    •	Thanks to the open-source community for continuous support and contributions.