To follow along with this chapter, you need the following installed locally:

• Node.js (>= v7.6.0) and NPM: You can find download and installation instructions for this on the Node.js official website (https://nodejs.org/en/).

If you use macOS, you can make use of the Homebrew package manager to install Node.js and MongoDB easily.

The code files of this chapter can be found on GitHub:
https://github.com/PacktPublishing/Server-Side-development-with-Node.js-and-Koa.js-Quick-Start-Guide/tree/master/Chapter02

Check out the following video to see the code in action:
http://bit.ly/2Q2gRoV

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.

Some of the key features introduced by ES6 include let, const, object destructuring, the spread operator, and so on. The async... await syntax, which is heavily used by Koa, is a new feature introduced in ES7. Some other key features introduced by ES7 are destructuring assignment (https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Destructuring_assignment) and Observables (https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/observe). Beyond ES6 and Es7, a lot of...

As JavaScript developers who may or may not have experience working with Node.js, a brief introduction to Node.js and its core ideology will help get everyone up to speed. Node.js, or simply Node, is a run-time environment that executes JavaScript outside a browser. In simpler terms, and as it relates to web developers, Node is a platform that allows developers to write JavaScript applications that can also act as servers.

JavaScript became popular for being a language used to manipulate the DOM (Document Object Model) on web pages. It was a language typically used for client-side scripting. Node, which was built on Chrome's open source v8 JavaScript engine, made it possible to run JavaScript both on the browser and the server. This was highly accepted, as developers could now develop applications with the same language on servers and web browsers.

Node is...

Asynchronous functions are functions that work asynchronously. They return a Promise class implicitly and can run concurrently. We will be discussing two major ways to define asynchronous functions. These include the following:

• Using the native Promise class
• Using the modern Async keyword

The await keyword is used inside an asynchronous function to resolve a promise. Async and await are usually used together for managing the control of flow in a modern asynchronous JavaScript application. Koa relies heavily on async.. await to avoid callback hell and provide a more convenient method for handling errors.

Before introducing async, let's discuss a little about the native Promise...

To install Koa, you need to have the following installed locally:

• Node (preferably > 7.6): This can be obtained from the Node homepage (https://nodejs.org/en).
• NPM: This is the official package manager for JavaScript and is usually installed along with the Node installation.

With Node and NPM installed, you only need to run this command on your Terminal to install Koa to your application:

npm install Koa

If you're using an older version of Node (< 7.6), you will need to use a transpiler such as Babel to make async functions compatible with your version of Node. Koa recommends using Babel's require hook, as seen in the example in the following code snippet (https://babeljs.io/docs/en/babel-register/):

require('babel-register');

// require the rest of the app that needs to be transpiled after the hook

const app = require('./app');

You can then install the transforms you would need, depending on your version of Node. If you are using V6 of Node, you would not need most of the transforms, since it already supports a lot of ES6 features. At the minimum though, you would need the transform-async-to-generator plugin. You can define this in your .babelrc file, as follows:

{
  "plugins": ["transform-async-to-generator"]
}

According...

To get started with starting a server in Koa, we should first create a project directory and enter that directory. We can do so with the following commands:

mkdir koa-server
cd koa-server

Next, we initialize a project in npm with the following command:

npm init

After running this command, follow the prompts to help create a package.json file for your project.

Next, we can install Koa to our project with the following command:

npm i koa

Now that we have Koa installed, we can create our server file. Let's call the file index.js. If you are using a Unix-based operating system such as Linux or macOS, you can create the file with the following command:

touch index.js

This file will serve as the entry point to our application, and we will write the main...

In this chapter, we learned about Node and how asynchrony in JavaScript works. We also learned about the different ways asynchronous actions in JavaScript are handled, including the async… await syntax.

After the primer, we dug into writing some code and started a very light server in Koa. This showed us the prerequisites of Koa, how to install the framework, and how to get started on it.

In the next chapter, we will learn about the core concepts of Koa. We will learn about the application, context, request, and response objects in Koa. We will also learn how to create and use middleware. We will go into details about Koa's philosophy and show readers how the different parts of the framework work.