C++, Python, JS, all these languages are using the same concepts and are very close in syntax in my opinion. Which means that if you learn properly one of them, you’ll be able to use the other ones. You’ll just need to adapt your knowledge to the context of the other languages, since you won’t do the same thing at all with them, you won’t use the same IDE, the same frameworks etc.
So instead of focusing on any specific language, ask yourself first what you want to do it with it. If you don’t care about web development, you should stay away from JS. If you want to code cool audio applications and plug-ins, just use JUCE with plain C++. If you want to focus on prototyping audio DSP, you might want to learn how to do it with Python, but you could create stuff way faster with Faust for example, or the script language in the DAW Reaper.
And if you care about what skill set will make more sense for future employement, then you might want to ask what are the tools used by some people in the companies you are interested in. All the plug-in developers are doing C++, and most of them don’t care about Python. In research laboratories and universities, people use python and/or Matlab, but not C++ that much etc.