Hello, readers!

This book assumes that you already know what React is and what problems it can solve for you. You may have written a small/medium application with React, and you want to improve your skills and answer all of your open questions. You should know that React is maintained by developers at Facebook and hundreds of contributors within the JavaScript community. React is one of the most popular libraries for creating user interfaces, and it is well-known to be fast, thanks to its smart way of touching the Document Object Model (DOM). It comes with JSX, a new syntax to write markup in JavaScript, which requires you to change your mind regarding the separation of concerns. It has many cool features, such as server-side rendering, which gives you the power to write universal applications.

To follow this book, you will need to know how to use the terminal to install and run npm packages in your Node.js environment. All the examples are written in modern JavaScript, which you should be able to read and understand.

In this first chapter, we will go through some basic concepts that are essential to master in order to use React effectively, but are straightforward enough for beginners to figure out:

• The difference between imperative and declarative programming
• React components and their instances, and how React uses elements to control the UI flow
• How React changes the way we build web applications, enforcing a different new concept of separation of concerns, and the reasons behind its unpopular design choice
• Why people feel the JavaScript fatigue, and what you can do to avoid the most common errors developers make when approaching the React ecosystem