IMHO TypeScript is the best mainstream language to write code in right now. It is incredibly expressive and feature rich, and you can model in almost any paradigm you like. The ecosystem around it allows you to choose whatever blend of runtime vs compile time type safety you prefer. Lots of people just runtime type check at their endpoint boundaries, and use compile time for everything internal to a service, but again, the choice is yours.

The Node+Express backend ecosystem is also incredibly powerful. Node is light weight, the most naïve code can handle a thousand RPS on the cheapest of machines, and you can get an entire server up and running with CORS+Auth+JSON endpoints in just 5 or 6 lines of code, and none of that code has any DI magic or XML configuration files.

JS/TS is horrible for numeric stuff, but it is great for everything else.