Introduction to Koa.js

What is Koa.js?

Koa.js is an open-source Node.js web framework designed by the developers of Express. This framework is designed to be a more compact, expressive, and stable base for web applications and APIs. Koa makes use of asynchronous functions to reduce the requirement for callbacks and improve error handling. Koa’s core does not include any middleware. It offers an improved set of ways for speeding up and exciting the server-building process.

Koa.js has following features

1. Koa.js makes advantage of ES6 generators to make synchronous programming and control flow easier.
2. In comparison to other Node.js frameworks, Koa.js has a minimal footprint. This allows developers to create middleware that is lighter.
3. Koa.js includes an error catchall to assist prevent website breakdowns.
4. A context object in Koa.js is a container for request and response objects.

Koa.js pros and cons

Pros :

Extremly lightweight

The sync/await keywords are supported, and they’ve made their way beyond generator functions.

No callback hell

Provide a good user experience.

Cons :

The community is quite small.

Express style middleware is incompatible.

Koa uses generators that are incompatible with any other Node.js framework middleware.

Koa Vs Express : Differences

Middleware chain : The Express middleware chain uses callbacks, whereas the Koa middleware chain uses Promises.

More lightweight : Koa is lighter than Express. Like Express, Koa does not feature router or view engine modules. These modules are available separately and can be readily combined.

Less popular : Express is more popular than Koa.

Cleaner syntax : For clearer code, Koa uses Generator functions and async/await. While this helps avoid “callback hell” when using Express in Node v7+, it’s less noticeable when using async/await with Express.

Creating a Server using Koa.js

To begin, create a new directory for your project. Then, using the terminal, navigate to the directory of your app and initialize your Node project from inside the directory.

npm init -y

After running the npm init command, you will have a package.json file with the default configuration.

Then run this command to install Koa

npm i koa

After that, use your favorite code editor to navigate to the index file in your app’s directory and write the code below to create the server.

const koa = require('koa')
const app = new koa()

app.listen(6850, () => {console.log('Server running on port 6850')})

Creating Routes using Koa.js

Koa.js, unlike Express, does not have routing by default. Instead, it uses the Koa Router middleware library. To implement routes in our server, we must first install the Koa router library.

npm install koa-router

Then, in your index file, import the Koa router module and add your preferred routes.

const koa = require('koa')
const koaRouter = require('koa-router')// importing Koa-Router

const app = new koa()
const router = new koaRouter()

router.get('home', '/', (context) => {
  context.body = "Welcome to the Koa.js Server"
})

app.use(router.routes())
  .use(router.allowedMethods())

app.listen(6850, () => console.log('Server running on port6850'))

Start the server and send a request from the browser to test the route.