I have completed a project which is completed on iOS and Android with all native code like in-app purchases and leaderboard completed. I want to convert that project into HTML 5 but without changing my C++ code to javascript and using the same resources. Is there any method/way to convert my code?
I was a native obj-c programmer who joined cocos2d-x porting from cocos2d-iphone. I have little/no knowledge of html or javascript.
If you want the resulting app to run within the browser, then no. There's no cocos2d variant that makes this possible. You would have to port the app to a completely different (but still C++) framework. See: How to build native C++ apps with HTML/CSS UI?
You can of course build a c++ app with cocos2d-x that presents a html5 view, but it won't run within the browser.