Katas are a set of challenges, and this resource has quite a few of them. You can read a book about ES6 and try to come up with solutions for this specifically tailored challenges. In this way, you won’t be terrorized by typical blog articles and tutorials with lousy challenges.
Lastly, there is one thing that you need to remember about Udemy courses. The moment you enroll in a specific course, you’re granted access to a special community page for that particular course. With this, you are able to connect with everyone else who has enrolled in the course. Also, this gives you the opportunity to learn material faster, as well as gain help whenever you need it.