IMO it's more like PHP or JavaScript than C++. With C++ there are lots of different dialects in common use and you kinda have to learn them all to be good at C++. Whereas with PHP/JavaScript/CSS there are still ugly corners, but everyone pretty much agrees which the good bits are and which the ugly bits are, and you can mostly just ignore the old legacy bits.
What part of JavaScript language should you not use?
The only one that comes to mind is is `with`, which is officially discouraged in the spec.
I suppose the other one is type coercion. (Like [] + [] stuff. That's no end of "ha ha JS weird.")
with, == (except certain idiomatic uses), __prototype__, eval, etc.