Introduction to Polka

Polka is a highly efficient and minimalistic routing framework for Node.js, designed to provide ultra-fast HTTP servers with minimal footprint. It is an ideal choice for developers seeking a lightweight alternative to Express without compromising on performance.

Setting Up Polka

To get started with Polka, you first need to install it via npm:

  npm install polka

Basic Usage

Creating a basic server with Polka is straightforward:

  const polka = require('polka');
  const { json } = require('body-parser');

  const { PORT=3000 } = process.env;

  const app = polka();

  app.use(json());

  app.get('/', (req, res) => {
    res.end('Hello, world!');
  });

  app.listen(PORT, err => {
    if (err) throw err;
    console.log(`> Running on localhost:${PORT}`);
  });

Using Middlewares

Polka supports middleware functions that can process requests before they reach the actual route handler. Here is an example:

  app.use((req, res, next) => {
    console.log(`Incoming request to ${req.path}`);
    next();
  });

Routing Parameters

Polka allows you to define route parameters easily:

  app.get('/user/:id', (req, res) => {
    res.end(`User ID: ${req.params.id}`);
  });

Query String Parameters

Handle query string parameters like this:

  app.get('/search', (req, res) => {
    const { query } = req;
    res.end(`Search Query: ${query.q}`);
  });

Handling Errors

Error handling in Polka can be done by passing an error to the next function:

  app.get('/error', (req, res, next) => {
    next(new Error('Something went wrong!'));
  });

  app.use((err, req, res, next) => {
    console.error(err.stack);
    res.statusCode = 500;
    res.end('Server Error');
  });

Combining Routes

You can modularize your routing logic by combining routes from different files:

  const userRoutes = polka()
    .get('/me', (req, res) => res.end('User Info'))
    .get('/:id', (req, res) => res.end(`User ID: ${req.params.id}`));

  app.use('/user', userRoutes);

Example Application

Here is a more comprehensive example that combines several aspects of Polka:

  const polka = require('polka');
  const { json } = require('body-parser');

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

  // Root Route
  app.get('/', (req, res) => {
    res.end('Welcome to Polka!');
  });

  // Middleware for Logging
  app.use((req, res, next) => {
    console.log(`[${new Date().toISOString()}] ${req.method} ${req.path}`);
    next();
  });

  // User Routes
  const userRoutes = polka()
    .get('/me', (req, res) => res.end('User Info'))
    .get('/:id', (req, res) => res.end(`User ID: ${req.params.id}`));

  app.use('/user', userRoutes);

  // Error Handling
  app.use((err, req, res, next) => {
    console.error(err.stack);
    res.statusCode = 500;
    res.end('Internal Server Error');
  });

  const { PORT=3000 } = process.env;
  app.listen(PORT, err => {
    if (err) throw err;
    console.log(`> Running on localhost:${PORT}`);
  });

Polka is a versatile and high-performance framework that makes building fast and efficient web applications a breeze. With its minimalistic design and powerful features, it is a compelling choice for Node.js developers.

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