Introduction to Koa Router

koa-router is a sophisticated routing module for Koa applications that enables developers to define robust and precise routing mechanisms for their applications. It provides a suite of useful APIs that are indispensable when building web applications with Koa.

Setting Up Koa Router

First, you need to install Koa Router:

npm install @koa/router

Then, integrate it with your Koa application:

 const Koa = require('koa'); const Router = require('@koa/router');
const app = new Koa(); const router = new Router();
// Sample route router.get('/', (ctx) => {
  ctx.body = 'Hello World';
});
app
  .use(router.routes())
  .use(router.allowedMethods());

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

Defining Routes

Let’s explore more routes and their usage:

 // GET route router.get('/hello', (ctx) => {
  ctx.body = 'Hello Route';
});
// POST route router.post('/data', (ctx) => {
  ctx.body = 'Data received';
});
// PUT route router.put('/update', (ctx) => {
  ctx.body = 'Data updated';
});
// DELETE route router.delete('/delete', (ctx) => {
  ctx.body = 'Data deleted';
});
// URL parameters router.get('/user/:id', (ctx) => {
  const userId = ctx.params.id;
  ctx.body = `User ID is ${userId}`;
}); 

Working with Query Parameters

Koa Router makes it simple to work with query parameters:

 router.get('/search', (ctx) => {
  const query = ctx.query;
  ctx.body = `Search query is ${query.q}`;
}); 

Handling Middleware

You can assign middleware to routes:

 const logger = async (ctx, next) => {
  console.log(`${ctx.method} ${ctx.url}`);
  await next();
};
router.get('/log', logger, (ctx) => {
  ctx.body = 'Logged route';
}); 

Nested Routes with Koa Router

Nested routes provide a hierarchical structure for routing:

 const parentRouter = new Router(); const childRouter = new Router({ prefix: '/child' });
childRouter.get('/example', (ctx) => {
  ctx.body = 'Child Route Example';
});
parentRouter.use('/parent', childRouter.routes());
app
  .use(parentRouter.routes())
  .use(parentRouter.allowedMethods());

Comprehensive Application Example

Here is an example integrating various features discussed:

 const Koa = require('koa'); const Router = require('@koa/router');
const app = new Koa(); const router = new Router();
// Home route router.get('/', (ctx) => {
  ctx.body = 'Home Page';
});
// User route with URL parameter router.get('/user/:id', (ctx) => {
  ctx.body = `User ID: ${ctx.params.id}`;
});
// Middleware example const auth = async (ctx, next) => {
  console.log('Authenticating...');
  await next();
};
router.post('/private', auth, (ctx) => {
  ctx.body = 'Authenticated content';
});
// Query parameter example router.get('/search', (ctx) => {
  ctx.body = `Search Term: ${ctx.query.term}`;
});
app
  .use(router.routes())
  .use(router.allowedMethods());

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

By leveraging these APIs and techniques, developers can create highly efficient and organized Koa applications. Whether you are building simple web applications or complex systems, Koa Router provides the tools necessary to streamline your routing logic.

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