@snehadatta/super-middleware

A collection of reusable Express.js middleware for:

• JWT Authentication
• Role-based Authorization
• Error Handling
• ETag-based Caching

Features

• jwtAuth – Authenticate users with JWT from cookies or Authorization header.
• roleAuth – Restrict access based on user roles.
• errorHandler – Centralized JSON error responses.
• notFoundErrorHandler – Consistent 404 responses.
• etagMiddleware – Adds ETag headers for GET requests to improve caching.

Installation

npm install @snehadatta/super-middleware

Quick Start

  import express from 'express';
  import {
    jwtAuth,
    roleAuth,
    errorHandler,
    notFoundErrorHandler,
    etagMiddleware
  } from '@snehadatta/super-middleware';
  
  const app = express();
  
  // Enable ETag caching
  app.use(etagMiddleware);
  
  // JWT Authentication
  app.use(jwtAuth(process.env.JWT_SECRET, async (userId) => {
    // Fetch user from DB
    return { id: userId, role: 'admin' };
  }));
  
  // Public route
  app.get('/', (req, res) => {
    res.send('Hello World!');
  });
  
  // Protected route
  app.get('/profile', (req, res) => {
    res.json({ user: req.user });
  });
  
  // Role-based route
  app.get('/admin', roleAuth(['admin']), (req, res) => {
    res.send('Welcome Admin!');
  });
  
  // 404 handler
  app.use(notFoundErrorHandler);
  
  // Error handler
  app.use(errorHandler);
  
  app.listen(3000, () => console.log('Server running on port 3000'));
  

API Reference

jwtAuth(secret, getUser)

Middleware to verify a JWT token and authenticate a user.

Parameters:

secret string - JWT secret key used to verify token

getUser function - Async function to fetch a user by decoded ID

Example:

app.use(jwtAuth('mysecret', async (id) => {
  return db.findUserById(id);
}));

roleAuth(allowedRoles)

Restricts access to routes based on user roles.

Parameters:

allowedRoles string[] - Array of allowed roles

Example:

app.get('/admin', roleAuth(['admin']), (req, res) => {
  res.send('Welcome Admin!');
});

errorHandler(err, req, res, next)

Centralized error handler for consistent JSON responses.

Usage

app.use(errorHandler);

notFoundErrorHandler(req, res, next)

Handles 404 Not Found responses in JSON format.

Usage

app.use(notFoundErrorHandler);

etagMiddleware(req, res, next)

Generates an ETag for GET responses.
If the If-None-Match header matches the ETag, sends 304 Not Modified.

Usage

app.use(etagMiddleware);

Contributing

Fork the repository

Create a feature branch:

git checkout -b feature/my-feature

Commit changes:

git commit -m "Add my feature"

Push and open a Pull Request

Support

If you encounter any issues or have questions, please open an issue for assistance.