This came to me, in the beginning. The confusion is to which one to pick first. It’s kind of chicken-egg problem.
Actually all these are interrelated and very dependent on each other, at least in the beginning.
If you are beginning, learn one of these three and keep moving and concentrating on only one for sometime. After a time, come back and start another. Now, that way worked for me and hope that works.
If you are reffering code, then also try and concentrate on one. Once you are fine with one, move to another one and concentrate on that one for the time you get comfortable on that one, then come back to code and refer the same codebase for the one you are concentrating now.
Hope that works and helps you get started with these technology.

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