5 ms·

I agree lukifer. Immutability is useful and interesting, but `const` in JS not really about immutability, it's about variable reassignment (which is trivial to

by sunseb 6y ago

I agree lukifer. Immutability is useful and interesting, but `const` in JS not really about immutability, it's about variable reassignment (which is trivial to handle really, even for a noob programmer). const arr = ['foo']; arr[0] = 'bar'; assert(arr[0] === 'bar'); // !!! Something like that would make sense though IMHO: const PHI = 1.618; I don't get how JS is designed really, they try to solve a bad design (`var`) but they introduce another bad design (`const`) and they make things even messier. Many devs ship JavaScript thought TypeScript these days, so I hope Microsoft can clean this mess one day.

madeofpalk 6y ago
What about const/let is poorly designed?
- sunseb 6y ago
  Have a look here: https://jamie.build/const https://jamie.build/const https://twitter.com/dan_abramov/status/1208369896880558080 https://twitter.com/dan_abramov/status/1208369896880558080 (React core team member) https://twitter.com/littlecalculist/status/917875241891676160 https://twitter.com/littlecalculist/status/91787524189167616... (Ember creator)
  - madeofpalk 6y ago
    I don't think it's poorly designed, its just maybe perhaps not all that useful?
    - karatestomp 6y ago
      Some people seem really unhappy that it might mean a reference is constant, rather than a value, if the value happens to be a reference. If that makes sense.
TechBro8615 6y ago
The issue I have with `const` is not your original premise, but the one you allude to here: people confuse reassignment and immutability. Because of this, they end up using const/let to "signify that they're not changing a variable," when it doesn't actually matter anyway, because they're thinking of immutability but disambiguating reassignment capability. You can usually tell who has only a superficial understanding of the language by reading how `const` and `let` are used in their code. Personally, I default to const, and use it pretty much 99.9% of the time. I use `let` in the few cases where it's actually useful to have a block-scoped variable. Ironically, this probably does a better job of "communicating" intent than the ritualistic obsession with "immutability" does, simply because you know if you're deviating from the default, there is a good reason for it.
lukifer 6y ago
Yeah, that's fair, I've been bitten by "not actually immutable" bugs before (works well enough for primitives, but not objects or arrays, which is most things in JS-land!). Libraries like Immutable.js can help bridge the gap. > they try to solve a bad design (`var`) but they introduce another bad design (`const`) `let` is intended to be the actual `var` replacement, and it's okay for that. I think there's an argument that `const` is a bad design, in the sense that it's deceptive, under the not-that-uncommon case you describe. Still, I'd rather have it than not, and I personally still like defaulting to `const` and opting-in to `let` in the (rarer and rarer) event that it's needed. (I'm also on 100% TypeScript at this point, which doesn't remove the potential for problems, but does provide an extra layer of guard rails in general.)
- sunseb 6y ago
  Yes, `let` is fine. I use `let` 99% of the time in my personal projects, it's more convenient, but I often must use `const` when working on an existing codebase. :( Most of JavaScript devs do like you, they default to `const` and if they need to reassign the variable, they switch to `let`. To me it feels more like a ceremony for declaring a variable than a rational and a useful practice. :)

by sunseb 6y ago

madeofpalk 6y ago

What about const/let is poorly designed?

sunseb 6y ago
Have a look here: https://jamie.build/const https://jamie.build/const https://twitter.com/dan_abramov/status/1208369896880558080 https://twitter.com/dan_abramov/status/1208369896880558080 (React core team member) https://twitter.com/littlecalculist/status/917875241891676160 https://twitter.com/littlecalculist/status/91787524189167616... (Ember creator)
- madeofpalk 6y ago
  I don't think it's poorly designed, its just maybe perhaps not all that useful?
  - karatestomp 6y ago
    Some people seem really unhappy that it might mean a reference is constant, rather than a value, if the value happens to be a reference. If that makes sense.

TechBro8615 6y ago

The issue I have with `const` is not your original premise, but the one you allude to here: people confuse reassignment and immutability. Because of this, they end up using const/let to "signify that they're not changing a variable," when it doesn't actually matter anyway, because they're thinking of immutability but disambiguating reassignment capability. You can usually tell who has only a superficial understanding of the language by reading how `const` and `let` are used in their code. Personally, I default to const, and use it pretty much 99.9% of the time. I use `let` in the few cases where it's actually useful to have a block-scoped variable. Ironically, this probably does a better job of "communicating" intent than the ritualistic obsession with "immutability" does, simply because you know if you're deviating from the default, there is a good reason for it.

lukifer 6y ago

Yeah, that's fair, I've been bitten by "not actually immutable" bugs before (works well enough for primitives, but not objects or arrays, which is most things in JS-land!). Libraries like Immutable.js can help bridge the gap. > they try to solve a bad design (`var`) but they introduce another bad design (`const`) `let` is intended to be the actual `var` replacement, and it's okay for that. I think there's an argument that `const` is a bad design, in the sense that it's deceptive, under the not-that-uncommon case you describe. Still, I'd rather have it than not, and I personally still like defaulting to `const` and opting-in to `let` in the (rarer and rarer) event that it's needed. (I'm also on 100% TypeScript at this point, which doesn't remove the potential for problems, but does provide an extra layer of guard rails in general.)

sunseb 6y ago
Yes, `let` is fine. I use `let` 99% of the time in my personal projects, it's more convenient, but I often must use `const` when working on an existing codebase. :( Most of JavaScript devs do like you, they default to `const` and if they need to reassign the variable, they switch to `let`. To me it feels more like a ceremony for declaring a variable than a rational and a useful practice. :)