4 ms·

On a side note, I find crazy this obsessive-compulsive behavior to use `const` everywhere in modern JS codebase (even in Webkit now). It solves really no probl

• lukifer 7y ago
  Immutability has been pretty hot of late, though still controversial. There are several popular languages which encourage or even force immutability (Elixir, Clojure). What sold me on the idea was Rich Hickey's talk, "The Value of Values": https://www.youtube.com/watch?v=-6BsiVyC1kM https://www.youtube.com/watch?v=-6BsiVyC1kM I look at it as mostly a safety net: I'd rather use const by default, unless I have a good reason to be able to mutate the variable. (To flip it around: what problem does being mutable-by-default solve?) 9 times out of 10, I don't need to change the value for the lifecycle of the function; and often if I do, the code is cleaner anyway if I use an immutable pattern (such as `const foo = bar.map()` rather than `for(x in bar) foo.push()`). Thanks to the magic of Merkle trees, we can generally make fresh pointers without it costing much memory overhead.
  • sunseb 7y 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 7y ago
      What about const/let is poorly designed?
      • sunseb 7y 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 7y 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.
• chadlavi 7y ago
  It's part of type enforcement for me (note: I do my work in typescript); if you never intend to redefine it, make it a const, then you'll get an error if you try to redefine it later. performance-wise, const is also around 20% faster than var, and usually faster than let (you can test it yourself: https://jsperf.com/let-vs-var-performance/67 https://jsperf.com/let-vs-var-performance/67). Edit: I forgot (because I always just write `const` anyway), but TSLint/VScode also default to bothering you to use const if you define a let/var and never re-define it.
• Chyzwar 7y ago
  There are very few places where you ever need to use let or var. const is solving important issues - it has lexical scope instead var function scope - it does not hoist like var - it prevents accidental reassignment Accidental reassignment happen more often in JS because of non-lexial scoping, weakly typed and async functions. Also, both Ruby and Python are "strongly typed" as opposed to weakly typed Javascript.
  • olliej 6y ago
    Let has lexical scope. I’ve always thought const was something of a mid feature, as it doesn’t generally do what people think. He’ll back when Opera was an actual browser engine it just used const as an alias for var.
• tobr 6y ago
  > So much brain power wasted on this useless thing. I can see the argument that using `const` over `let` doesn’t bring any huge benefits, but I don’t see what the harm is either. I never found it a waste of brainpower. At this point it’s idiomatic, so I think using `let` everywhere is more likely to have people confused.
  • megous 6y ago
    It's nice until you want to reassign some global variable externally for in-production debugging via a browser console.