Next-generation web framework for node.js (Koa.js)

The Express development team created Koa.js, an open-source Node.js web framework. As their official website says, the framework aims to be a smaller, more expressive, and more robust foundation for web applications and APIs.Koa considerably enhances error handling and helps do away with callbacks through the use of asynchronous functions. Koa’s core does not include any middleware. It offers a sophisticated set of techniques that expedite and enhance the server-making process.

Who uses Koa.js?

The Koa.js framework is widely used by businesses for their websites and online APIs. Here is a list of the top five Koa.js framework users from across the world.

1. Paralect
2. Pubu
3. Bulb
4. GAPO
5. Clovis

Features of Koa.js

Koa.js has its own special features that make it more expressive and developer-friendly, much like all other accessible frameworks. Here are a couple of Koa’s best features.

1. It is modern and futuristic.

Koa.js is modern and future-proof Unlike other Node.js frameworks, Koa.js build is based on ES6 which makes the development of complex applications simpler by providing a bunch of new classes and modules. This helps developers in creating maintainable applications.

2. It has a small footprint.

Koa.js is less in weight than other Node.js frameworks. This aids in the creation of middleware that is lighter and more effective. However, they do have the choice to add additional modules to the system to make it larger to accommodate the demands of varied projects.

3. It uses ES6 generators

Koa.js leverages ES6 generators to make synchronous programming easier and to improve control flow. In order to manage the execution of code on the same stack, these generators can also be utilized as functions.

4. Better Error handling

Koa.js enhances error handling by leveraging middleware more effectively. The framework’s integrated error catchall helps developers prevent website failures. Programmers can report failures even without generating additional code by using the straightforward “try/catch” function. Koa.js error handling may also be customized by developers by only changing the default configuration.

5. It uses a context object

Additionally, Koa.js aids developers in using Context to combine the standard response and request objects into a single object. By incorporating a variety of practical methods and assessors, the unified object facilitates the development of web apps and APIs. With several approaches for creating web apps and APIs, this context is a NodeJS object that combines the request and response into a single object.

Pros of Koa.js

1. Koa makes middleware development more enjoyable while enhancing interoperability and robustness.

2. Koa has only 550 lines of code, making it quite compact.

3. By getting rid of the confusion brought on by all those callbacks, ES6 generators will organize the code and make it easier to handle.

4. It offers an excellent user experience.

5. More comprehensible and cleaner async code.

6. No callback hell

Cons of Koa.js

1. There is a comparatively tiny open source community.

2. Incompatible with middleware in the Express style.

3. Koa uses generators that are incompatible with every other middleware for the Node.js framework.

Express.js vs Koa.js

Because both Koa.js and Express.js were created by the same team, working on them is comparable. Due to the lack of middleware and superfluous boilerplate code, Koa is a relatively light and flexible system that can be molded to meet the application requirement. The application becomes more modular when libraries are used.

Koa uses async features and promises to eliminate callback hell and streamline error handling. It exposes its own ctx.request and ctx.response objects in place of the node’s req and res objects.

While Koa lacks several framework capabilities like routing and templating, Express enhances the req and res objects in node by adding new attributes and methods.

How is Koa different from Express?

1. No callback hell
2. No boilerplate codes were used
3. Improved user experience all around
4. Using try/catch, error handling is improved
5. Koa is less dependent on middleware.
6. Koa has more modularity.
7. Routing is not offered, in contrast to Express.
8. Stream handling techniques

Creating a server using Koa.js framework

Let’s get practical and learn how to build a basic server using Koa.js now that we have a better understanding of what it is and some of its capabilities.

Create a new directory for your application first, then use the terminal to browse to it and perform the following command:

npm init

To create a Node.js package.

Then run to install Koa.js

npm i koa

Afterward, navigate to the index file on your app’s directory using your favorite code editor and write the code below to create the server.

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

app.listen(2400, () => {console.log('Server running at PORT 2400')})

The code used to create the server is pretty straight forward, just import the koa module and use its listen method. To start the server, run node ’name of your index file’ on the terminal.

Creating routes using Koa.js

Unlike its predecessor, Express, Koa.js does not handle routing by default. Instead, it uses a middleware library Known as Koa Router. So, to implement routes in our server, we will first need to run the snippet below to install Koa router library.

npm install koa-router

Then import the Koa router module onto your index file and add your desired routes. Below is a code example to demonstrate route creation using Koa.js.

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 my Koa.js Server"
})

app.use(router.routes())
  .use(router.allowedMethods())// registering routes to the application

app.listen(2400, () => console.log('Server running at PORT 2400'))

Start the server again and test the route by sending a request from the browser.

Handling Responses in Koa.js

As we mentioned earlier, Koa response objects are embedded in its context object. This means that we access the response object from the context object. Let’s use a route definition like the one above to demonstrate handling responses.

router.get('home', '/', (context) => {
  context.status = 200 //This is the response status
  context.body   = "Welcome to my Koa.js Server" // This is the response body
})

Handling errors in Koa.js

To handle errors in Koa, add an error middleware early in your index file. It must be defined early because only errors defined after the middleware can be caught. The code below includes the error middleware in our server.

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

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

app.use( async (ctx, next) => {
  try {
    await next()
  } catch(err) {
    console.log(err.status)
    ctx.status = err.status || 500;
    ctx.body = err.message;
  }
})

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

app.use(router.routes())
  .use(router.allowedMethods())// registering routes to the application

app.listen(2400, () => console.log('Server running at PORT 2400'))

To test this let’s modify the home route method to throw an error when the route is called.

router.get('home', '/', (context) => {
  context.throw('Sample error message', 500)
})

Now run the server again and call the endpoint using a browser.

Summary

In this article, we learned about Koa.js, including its definition, capabilities, and how to use it to build servers. We have tested its distinctive syntax and several of its new capabilities by building a straightforward server. The New Node.js framework Koa.js has been embraced by a number of well-known enterprises on a worldwide scale. Any web developer interested in experimenting with a new framework should think about Koa.js.

If you want to find out more about Koa.js, refer to its website or find it on GitHub

https://youtu.be/5wARfYSwI2M?si=yH_gn62ozyk_4vi8

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Follow me on GitHub: Madhusha Prasad

example repo