How to check type of a C++ object or if it is NULL from JS?

Cocos2d-x
#1

I have some experienced with Cocos2d-x Lua and I used to call tolua.isnull( yourObject )
or tolua.type( yourObject) for debug or some condition.

I wonder if Cocos2d-x JS have such helpful stuff like Lua does?

If it does, how to use it?

It seemed there aren’t any documents about it.

Thanks