Before we get into Node.js and writing code in Koa, we should take a quick look at the modern JavaScript ES6, ES7 (and beyond) syntaxes and the advantages they bring. ES6 (or ES 2015) and ES7 (or ES 2016) are major updates to the JavaScript language that brought a lot of new features and optimized the language for readability and simplicity.
The introduction of modern syntaxes and functions have made it possible for JavaScript developers to write concise and maintainable code, without the need to sacrifice performance. On the contrary, a lot of the new features make it possible to do more things in the language. Some of these things were done in the past using external libraries that exposed helper functions. Examples of such libraries include Lodash and Underscore.js.
Most code examples in this book use the newer ES6/ES7 JavaScript features. Ensure you have a recent version of JavaScript running on your machine so as to be able to follow along adequately.