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Comment by earthboundkid | Hacker News Reader

Basically all uses of const in JavaScript are pointless. I have asked many times for someone to show me an example of a bug that shipped that would have been prevented by const as it exists in JS. I'm still waiting.

The only time I can think of where const is useful is in Vue 3, it lets you ensure that you remember to change myref.value instead of trying to reassign myref by mistake. But it's just sort of a coincidental side effect of the fact that Vue reactivity has to work by mutating properties and not rebinding names. Plus Evan You is experimenting with a syntax transform to make it not necessary to use .value anyway.

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>Basically all uses of const in JavaScript are pointless. I have asked many times for someone to show me an example of a bug that shipped that would have been prevented by const as it exists in JS. I'm still waiting.

You have it backward; there's almost never a need to use let in JavaScript, as most variables should never be reassigned.

I've seen bugs pop up many times in client-side development where, for whatever reason, a variable is reassigned in a way that's difficult to predict. By defaulting to const unless reassignment is necessary, you're essentially putting documentation into the actual code and you can prevent logic errors by forcing runtime errors during development.

> as most variables should never be reassigned.

Why not? Reassigning globals can lead to bugs, sure. But when does reassigning a local lead to bugs?

> By defaulting to const unless reassignment is necessary, you're essentially putting documentation into the actual code

No, by defaulting to const, you're removing documentation. "Does this variable need to be kept safe from reassignment? Is it ever used again after this point in the code? Or is the developer just blindly using const for no reason?" Gotta read the code to figure it out because now const is just meaningless noise.

The same argument has been used against the use of TypeScript, and it is a fair argument. If someone has never had a problem involving types, or a variable being mistakenly set to the wrong value, then they will have higher confidence in not using TypeScript or the `const` keyword.

`const` isn't exactly that useful, especially considering that the tooling most of us use now helps us catch these sort of mistakes before runtime, but there's basically no objective reason to not use it. If you have a value that you don't want to change, `const` is only a few extra bytes from `let` and will provide better feedback when your tests fail because a value was subsequently set when it shouldn't have been. Maybe that never happens to you, but just because it's a rare problem doesn't mean it's useless to take a precaution. Most of us will never get into a car accident, but that doesn't mean that airbags are useless.

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