Hi guys,
I’m starting to learn cocos2d now, but my current macbook is really slow, it can’t handle XCode, I don’t have an Android device, nor a Apple Developer License. I’ll have a better computer in a few weeks, but if I start now with html5, will this knowledge be usefull when I move on to C++?
Thanks 
Of course.
Cocos2d-html5 was developed base on cocos2d-x. They are similar to each other.
If you are freshman to Cocos2d, I suggest you start with testcase and helloworld.
It depends what you mean by “move on to C**". When you say "move on to C**” what is your goal? Javascript is not C**, they are different languages… whether it is useful knowledge when you move on to C** is highly dependent on the circumstances.
Cocos2d knowledge is useful for all of the branches because of how similar it is written across the board.
If you mean… “will this knowledge be useful when you use cocos2d-x with C++” then yes, it is very useful knowledge.