>C++ has terrible performance anyway.

In terms of what?
It's built out of C, in fact you can if you want to just strip it down just to use C functions.

So I'm not really understanding this statement. Give me example where performance is lacking.

Now comparing to assembly, I can understand but native C++ shouldn't be that different.

>Your point of reference must be JavaScript

Nope, mine is C, C++, C#, and Java in that order.