Data Validation Library

A simple and lightweight data validation library for JavaScript, designed for use in Node.js applications. This library allows you to define validation rules for different fields and then validate data against those rules.

Installation

You can install the Data Validation Library via npm:

npm install data-validator

Usage

First, require the library in your Node.js application:

const DataValidator = require('data-validator');

// Create an instance of DataValidator
const validator = new DataValidator();

Adding Validation Rules

You can add validation rules for different fields using the addRule(fieldName, ruleFunction) method. The ruleFunction should return an error message if the validation fails, otherwise null.

validator.addRule('username', value => {
  if (!value) {
    return 'Username is required';
  }
  if (value.length < 3) {
    return 'Username must be at least 3 characters long';
  }
  // Additional rules can be added here
});

validator.addRule('email', value => {
  if (!value) {
    return 'Email is required';
  }
  if (!isValidEmail(value)) {
    return 'Invalid email format';
  }
  // Additional rules can be added here
});

Validating Data

To validate data against the defined rules, use the validate(data) method. It returns an object containing validation errors, if any.

const userData = {
  username: 'john_doe',
  email: '[email protected]'
};

const errors = validator.validate(userData);

if (Object.keys(errors).length === 0) {
  console.log('Data is valid!');
} else {
  console.log('Validation errors:', errors);
}

Helper Function

You can define helper functions to assist in validation, such as validating email format:

function isValidEmail(email) {
  // Regular expression for email validation
  const emailRegex = /^[^\s@]+@[^\s@]+\.[^\s@]+$/;
  return emailRegex.test(email);
}

License

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