Mainly because of code reuse. I need OpenGL to handle graphics and 2D animations.

This seems like a good choice as I know C++ and its known for portability:
https://msdn.microsoft.com/en-us/library/dn707591.aspx

However, it does not seem to be able to port over to web app?

Any suggestions? Quite a noob here to cross-platforming.

Thanks.