light-express-validator

light-express-validator is a homemade lightweight validation middleware for Express.js applications. It allows you to easily validate incoming request data with a simple and intuitive syntax.

1. Why light express validator?

• It's simple to use, lightweight and 0 dependency.

Installation

To install the package, run:

npm install light-express-validator

Usage

Basic Usage

1. First, require the package in your Express.js application:

const validate = require('light-express-validator');

2. Define your validation rules for each field you want to validate:

const validationRules = {
  username: 'required|min:3|max:20',
  email: 'required|email',
  age: 'required|numeric|min:18',
};

3. Use the validate middleware in your route:

app.post('/user', validate(validationRules), (req, res) => {
  // Your route handler logic here
});

Available Validation Rules

• required: Field must be present and not empty
• min:x: Field must have a minimum of x characters
• max:x: Field must have a maximum of x characters
• numeric: Field must be a number
• integer: Field must be an integer
• decimal:x: Field must be a decimal with x decimal places
• boolean: Field must be true or false
• date: Field must be a valid date
• email: Field must be a valid email
• image: Field must be an image file (for file uploads)

Handling Validation Errors

If validation fails, the middleware will automatically send a 400 Bad Request response with detailed error information. The response will have this structure:

{
  "name": "ValidationError",
  "fields": {
    "name": "The name field must be at most 9 characters.",
    "email": "The email field must be a valid email address."
  }
}

Custom Error Handling

If you want to handle validation errors differently, you can catch the ValidationError:

app.use((err, req, res, next) => {
  if (err instanceof ValidationError) {
    // Custom error handling logic
    return res.status(422).json({ errors: err.fields });
  }
  next(err);
});

Example

Here's a complete example of how to use light-express-validator in an Express.js route:

const express = require('express');
const validate = require('light-express-validator');

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

app.post(
  '/user',
  validate({
    username: 'required|min:3|max:20',
    email: 'required|email',
    age: 'required|numeric',
  }),
  (req, res) => {
    // If we reach here, validation passed
    res.json({ message: 'User created successfully', user: req.body });
  }
);

app.listen(3000, () => console.log('Server running on port 3000'));

This setup will validate that:

• username is required, at least 3 characters, and no more than 20 characters
• email is required and a valid email format
• age is required, numeric

If any of these validations fail, it will return a 400 Bad Request with details about which fields failed validation.