To help you practice during the whole duration of the course, we use the CodePen interactive online editor. CodePen is an HTML, CSS, and JavaScript code editor that previews/showcases your code bits in your browser. It helps with cross-device testing, real-time remote pair programming and teaching. Here's an article of interest if you use CodePen: Things you can do with CodePen [Brent Miller, February 6, 2019].
We also seldomly use JS Bin, an open source collaborative Web development debugging tool. Tutorials can be found on the Web (such as this one) or on YouTube. The tool is really simple: just open the link to the provided examples, look at the code, look at the result, etc. And you can modify the examples as you like, you can also modify / clone / save / share them. Keep in mind that it's always better to be logged in (it's free) if you do not want to lose your contributions/personal work.