Here I see the following:
.... the team of Cocos2d-x are working on something called "Javascript binding for Cocos2d". What that means is your very same code running on Cocos2d-html5 engine can work flawlessly on Cocos2d-X and Cocos2d-iPhone without or with little modification. And all that translates to "almost native fast on mobile phones".
What I can not understnad is that how the code written in one language can be translated to another one? Do they mean that there is a tool that gets as an input JavaScript code of Cocos2d-html5 game and translate it to C++ Cocos2dx code or backwards?
EIDT: Can I port easily the C++ game written with Cocos2Dx into Cocos2D-html5? What I have to do for that?