The beauty of `const` in JS is that it's almost completely irrelevant. Not only does it have nothing to do with immutability, it's also local. Which means, if I were to write `let` instead of `const`, I could still see whether my code reassigned that variable at a glance. The keyword provides very little in the way of a guarantee I could not otherwise observe for myself.

Immutability is completely different. Determining whether a data structure is mutated without an actual immutable type to enforce is impractical, error-prone, and in any event impossible to prove for the general case.