I prefer this to be a casual competition, where everyone can learn from any challenge, rather than those provided just for the sake of winning. That's the role of HackerRank, which I don't find very practical in the real work market.

I would say js is so much easier and the learning curve is far lower than C. However, you need to get around to frameworks or libraries, as plain javascript has almost no place in the current market.

I don't understand why you dislike new stuff like (let, const and arrow) functions. Coming from the an OPP background (java and C++), these sorts of things make JS more reasonable for programmers than how it was when "var" was the only option (which completely neglects the concept of scope) and you had to manually bind functions in a lot of complex scenarios.

JavaScript is single threaded and cannot offer the top notch performance compared with other programming languages, even with many tweaks developers have improved JS with like "Async" which is used to mimic the process of creating a new thread, though it is not in reality. I'm not sure about python as I haven't used it much though.

Adding to what others have said, I would say you can also learn other lower level programming languages first, in order to have a real "feel" how to to code efficiently. I am saying this because javascript (including node.js) is a high level language, and you may do stuff inefficiently because you let the program do all sort of tricks for you (E.g. in js, you don't have to care about even the size of an array or efficiently manage an array. No sort of concept for different types of collection exists, just almost always about arrays).