The problem is that, when prototyping and iterating a design I often don't know in advance what should be private or const and what shouldn't be. And when interactively experimenting in the DevTools console I often want to redefine `const shadowMapSize=1024` to `shadowMapSize=2048` but const breaks interactive console redefinition. I have to save the js file to disk and edit shadowMapSize there, then reload the code. This is the workflow for a static language like C++, not a dynamic language like Lisp or JavaScript.