What is Koa.js?

As a cross-platform server-side runtime environment, Node.js makes it easier for web developers to build fast and scalable network applications with JavaScript. At present, many web developers even use Node.js to write both frontend and backend of a web application in JavaScript. The web developers can further accelerate development of custom web applications and application programming interfaces (APIs) by using a number of Node.js frameworks.

Koa.js is a widely used Node.js web application framework. Koa.js is developed and maintained by the creators of another widely used Node.js framework — Express.js. As a lightweight Node.js framework, Koa.js provides a minimal interface for developing web applications and APIs. The features and tools provided by the framework further help programmers to accelerate development of web applications and APIs.

Features that Differentiate Koa.js from Other Node.js Frameworks

Small Footprint

Koa.js is designed as a lightweight and flexible framework for Node.js. Hence, it has a smaller footprint than other Node.js frameworks. While developing server side apps, many developers use Koa.js to write thinner and better middleware. However, they still have option to extend the framework according varying project requirements by plugging in a wide range of modules.

Modern and Futuristic

Unlike conventional Node.js frameworks, Koa.js is built based on ECMAScript 6 or ECMAScript 2015 specification. ECMAScript 2015 simplifies development of complex application by providing a number of new classes and modules. Koa.js also uses generators which are a part of ECMAScript 2015 specification. Hence, it helps developers to create applications that remain relevant over a longer period of time.

Generators

As noted earlier, Koa.js uses an ECMAScript 2015 specification — generators. In addition to simplifying synchronous programming, generators further facilitate both upstream and downstream flow of controls. The developers can even use generators as functions to stop and resume code execution with the same stack. Hence, they can easily improve a web application’s performance by executing script in a customized order.

Error Handling

While writing web applications, programmers explore ways to identify and handle errors more efficiently. Koa.js both simplifies and improves error handling by using middleware more effectively. The built-in catchall for errors provided by the framework helps developers to prevent website crashes. The programmers can even use a simple ‘try/catch’ command to log errors without writing additional code. Koa.js even allows developers to customize error handling simply by changing the default setting.

Cascading Middleware

While using Node.js, programmers have to write additional code to streaming a file and closing the stream. But Koa.js helps programmers to avoid writing additional code by passing the file instead of streaming the file. A programmer can use the yield next command to yield requests downstream and send back responses upstream. He can further pass the streams manually according to his precise needs.

Router Module

Most web frameworks provide scripts, images, HTML pages, and other website resources through different routes. But the core module of Koa.js does not support routes. The web developers have to use Koa-router module to create multiple routes for various website resources. They can install the Koa-router module simply by running a command. The developers can even use the module to create both static and dynamic routes.

HTTP Methods

Koa.js identifies and understands the operation required by a client through HTTP methods like GET, POST, PUT and DELETE. Hence, the developers need to ensure that each request sent from the client includes the appropriate HTTP method. For instance, a request to retrieve data must contain the GET method, whereas a request sent to the server to accept enclosed data must include the POST method.

Request Object

Koa.js uses a request object developed on top of the vanilla request object provided by Node.js. But the request object uses by the framework accelerates HTTP server development by providing a number of additional functionality. The developers can even use the object to access various properties of a request — header, path, method and URL.

Response Object

The response object used by Koa.js is developed based on the vanilla response object provided by Node.js. But the Koa response object, like Koa request object, provides a number of additional functionality. The developers can even use the object to access important properties of a response — header, body, message and status.

Context

In addition to enhancing the vanilla response and request object provided by Node.js, Koa.js further allows developers to encapsulate the vanilla response and request objects into a single object using Context. The unified object helps developers to build web applications and APIs more efficiently by using a number of helpful methods and accessors. The JavaScript developers even have option to create a context per request and refer the context as the receiver in the middleware.

However, the JavaScript developers must install Node.js and node package manager (npm) on their systems to leverage the features and tools provided by Koa.js. But they must use the frameworks to build applications rapidly and keep the applications relevant in the long run. They can even use various modules to extend and customize Koa.js according to precise needs of each project.