I took a quick look at Microsoft Introduction to ReactJS, not to actually learn React, but to evaluate how good the materials are for a beginner to learn React.

tl;dr
Avoid the assessment. Maybe use create-react-app instead of codepen.
Covers the basics quite well.

Lesson 01 | JSX and React Components

Instead of using “create-react-app” as a starting point, the course tells you to go to codepen to check out react.

I guess that makes it a little more focused on the React concepts and less focused on all the surrounding technologies that are needed in an production environment.

After that it covers the basics of ReactJS, and JSX.

If you are a beginner you probably want to check out create-react-app.

Lesson 02 | State, Life Cycle and Event Handlers

I think the chapter covers the basics quite well. Nothing really to add here.

Lesson 03 | Lists and Forms

Here i think it is very nice that they cover the basics of handling multiple Form Elements with a generic handler.

Assessment

The Assessment is quite theoretical and asks rather complicated questions. These questions are especially hard if you have already worked with React as you would never even try to build something in that way.

As a beginner I would completely skip the Assesment. It does not help you to further your understanding of React. It actually also confronts you with bad practices, while inferring that this would be the way how you would actually do things

Conclusion

If you use create-react-app with vscode I think you would have a much better starting experience.
The course is great to get started with ReactJS, if you avoid the assesments and rather just experiment with your own code base.