You have an application that you have been using in your own computer during development. How do you put this application in front of your users? In this chapter you are going to learn how to work with production builds of your application.

Up to now, all the testing done on the application you've built was manual. Manual testing as you develop your application is useful, but as the application grows the required testing effort grows as well, until it becomes so time-consuming that the only way to keep up is to test less, or to find a way to automate some testing work. In this chapter you are going to learn some techniques to create automated tests for your React application.

An important part of React that you haven't seen yet is memoization, a technique that helps prevent unnecessary renders and improve the overall performance of the application. In this chapter you are going to learn how the React rendering algorithm works, and how you can make it work efficiently for your application.

By now you have learned most of the React concepts you need to complete this application. This chapter is dedicated to building the remaining features of the application, with the goal of solidifying the knowledge you acquired in previous chapters.

Up to this point, you have been using the Microblog API back end with an option to bypass authentication. This enabled the project to grow without having to deal with the highly complex matter of user authentication up front. In this chapter you will finally learn how to do this.

A big part of most web applications is accepting, validating and processing user input. In this chapter you are going to learn how to perform these tasks with React by creating the user registration and login forms for Microblog.

In Chapter 5, the Posts component was modified to make an API call that gets data from the server. The way it was done, however, does not scale very well, because as the application continues to grow, there's going to be other components that will also need to make their API calls, and having to repeat the API calling logic in several places will be difficult to manage, especially considering that these calls are going to become more complex once authentication and pagination are implemented.

In this chapter you are going to learn how the React application can communicate with a back end application to request data. While doing this, you will learn how to use the two most important React hooks: useState() and useEffect().

React is a Single-Page Application (SPA) framework, which means that from the point of view of the browser, only one web page is ever downloaded. Once that page is active, all the application state changes will happen through JavaScript events, without the browser having to fetch new web pages from the server. How then, can the application support page navigation?

In Chapter 2, you wrote your first React component. In this chapter you will delve deeper into React as you learn how to create robust applications by combining and reusing components, not only your own but also some imported from third-party libraries.