[rpastuszak]

However, it's worth noting that using const doesn't make variables immutable. It only protects them of being reassigned:

const val = 'a'; val = 'b'; // TypeError

const obj = { val: 'a' }; obj.val = 'b'; // This line will still work.

obj = { val: 'b' }; // TypeError

[dcherman]

Yep. In those cases, I still prefer let personally even though I know the variable itself will not be re-assigned, kind of as an indicator that I expect the referenced object to be mutated.

[candu]

Coming from a background that includes some experience with C / C++, `const` here works as I expect it to. I'd prefer `const` even for the object reference case: I get errors on reassignment this way, and presumably it makes additional optimizations possible. To each their own, I suppose :)

There's also `Object.defineProperty()`, `Object.freeze()` for more control over mutability.