John Carmack on mutable variables

I also default to const in javascript. Somehow a "let" variable feels so dirty, but I don't really know why. I guess at this point my experience forged an instinct but I can't even put a theory on it. But it's sometimes necessary and I use it of course.

In JS, by using const, you are signalling to the reader that they don’t need to look out for a reassignment to understand the code. If you use let, you are saying the opposite.

JS's const doesn't go far enough since you can still mutate the object via its methods. In C++, you can only call const methods (which can't mutate the object) on const variables.