React.js Fundamentals is a free course, offered along with another course (ES6/7 for React, $45) and some upcoming paid courses in McGinnis' React.js Program. The Learn React.js: The Basics course ...

Now, here’s where the special nature of React comes in. Besides normal HTML, CSS, and JavaScript, the bulk of your React code will be written in JSX.

The React project originated at Facebook; the open source project has a BSD license and a patent rights grant from Facebook. React is not an end-to-end JavaScript application framework.