Introducing Koa

Node.js, which was introduced in 2009, has become very popular for building applications and APIs on the web. One of the major factors that influenced its increase in popularity is the fact that developers can now use a single language for developing their applications, both on the server side and client side. JavaScript developers who usually only worked on client-side applications in the past could now work on server-side applications with the same development stack. This increase in popularity and adoption has led to a lot of community enthusiasm and support, which by extension has caused a lot of frameworks and plugins being developed to optimize scripting and software development in Node.js.

Many of these frameworks are focused on different ideologies and functionalities. Express.js, with over four million weekly downloads as at the time of writing, is one of the more popular frameworks for Node.js. It was built to be a very simple and unopinionated framework for quickly building out web applications in Node.js. Koa.js was built to be an improvement on Express.js, with the same underlying philosophy.

Since its introduction, JavaScript has continually evolved and every iteration brings with it advantages and upgrades. Koa leverages on a lot of new and shiny things in the newer JavaScript versions, such as the async... await syntax. These features are part of what makes Koa a fast and easy-to-use web development tool.

The topics that will be covered in this chapter are the following:

• What is Koa?
• What can you do with Koa?
• Why choose Koa?
• When you should not use Koa
• Introducing Koa2
• Koa versus Express
• How can this book help you understand Koa better?