It's a bit unclear what you mean when you say "what can I do". If you're referring to specific language features that are available to Java or C++ that are not available to JavaScript, it would be ...

JavaScript is the most in-demand programming language for developer jobs and one of the most versatile languages for full-stack development. Here's what you need to know about JavaScript.

Do you really need a DXP or can you get by building front-end experiences based on JavaScript and microservices?