express-validator

What is express-validator?

express-validator is a set of express.js middlewares that wraps validator.js, a library for string validation and sanitization. It provides a comprehensive set of validation and sanitization middlewares for handling user input in express applications.

What are express-validator's main functionalities?

Validation

This feature allows you to validate user input. In this example, the 'username' field must be alphanumeric and the 'password' field must be at least 5 characters long. If the validation fails, a 400 status code with the validation errors is returned.

const { body, validationResult } = require('express-validator');

app.post('/user', [
  body('username').isAlphanumeric(),
  body('password').isLength({ min: 5 })
], (req, res) => {
  const errors = validationResult(req);
  if (!errors.isEmpty()) {
    return res.status(400).json({ errors: errors.array() });
  }
  res.send('User is valid');
});

Sanitization

This feature allows you to sanitize user input. In this example, the 'email' field is normalized to a standard email format and the 'username' field is trimmed of whitespace and escaped to prevent HTML injection.

const { body } = require('express-validator');

app.post('/user', [
  body('email').normalizeEmail(),
  body('username').trim().escape()
], (req, res) => {
  res.send('User input is sanitized');
});

Custom Validators

This feature allows you to create custom validation logic. In this example, the 'age' field must be at least 18. If the validation fails, a 400 status code with the validation errors is returned.

const { body, validationResult } = require('express-validator');

app.post('/user', [
  body('age').custom(value => {
    if (value < 18) {
      throw new Error('Age must be at least 18');
    }
    return true;
  })
], (req, res) => {
  const errors = validationResult(req);
  if (!errors.isEmpty()) {
    return res.status(400).json({ errors: errors.array() });
  }
  res.send('User is valid');
});

Other packages similar to express-validator

joi

Joi is a powerful schema description language and data validator for JavaScript. It allows you to create blueprints or schemas for JavaScript objects to ensure validation of key information. Compared to express-validator, Joi is more focused on schema-based validation and is not tied to express.js.

yup

Yup is a JavaScript schema builder for value parsing and validation. It is similar to Joi but is more lightweight and has a more modern API. Like Joi, Yup is not tied to express.js and can be used in various JavaScript environments.

validator

Validator is a library of string validators and sanitizers. It is the underlying library used by express-validator for its validation and sanitization functions. While it provides a comprehensive set of validation and sanitization functions, it does not provide middleware for express.js out of the box.

README

express-validator

An express.js middleware for validator.

• Installation
• Documentation
• Changelog
• License

Installation

npm install express-validator

Also make sure that you have Node.js 8 or newer in order to use it.

Documentation

Please refer to the documentation website on https://express-validator.github.io.

Changelog

Check the GitHub Releases page.

License

MIT License