What are some good resources and learning methods to become a back-end engineer in Node.js?
I would always use Node.js for my side projects, and I felt like the Heroku starter guide for it was good. However, Heroku recently removed its free tier, so I'm unsure where to go now if you want to do stuff for free.
When it comes to learning method, I recommend just building stuff and deploying it. I'm assuming you want to use Node.js to build REST APIs - That's something very sharable. After you build the API, you can couple it with a Postman collection so others can try it, or better yet, make an API explorer website that lets users make calls to your API with a simple, friendly GUI.
Aside from that, attaching more context to your question would help a lot with more targeted responses. Some questions for you: