This article is not going to cover what React is or why you should learn it. Instead, this is a practical introduction to the fundamentals of React.js for those who are already familiar with JavaScript and know the basics of the DOM API.
You should use this guide as a companion to the official Facebook documentation for getting started. While the official docs are great, the React ecosystem includes many other important projects which are outside the scope of the React docs.
Now don’t get me wrong, this doesn’t mean I can turn you into a React master instantly. But at least you’ll understand all the major concepts, if you do decide to jump in.