There are two approaches for reference:
It is supported by Cocos2d-x v2.1.4. You may find it in the stable release zip ball. What you need to do just recompile it again.
It will save your time, however, the converted code isn’t human readable.
Rewrite it in Cocos2d-html5. It is easy to port, because the api is the same.
For short term, approach 1 is better, for middle term or long term, I suggest approach 2.