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'class' is one of the most commonly mentioned but least useful constructs available in ES6. Things that win out over it? Destructured assignment, sane module sy

'class' is one of the most commonly mentioned but least useful constructs available in ES6. Things that win out over it? Destructured assignment, sane module syntax, arrow functions, true block scope variable declaration, and constants.

Cshelton 11y ago
Yes, but people coming from java or c# or something will like it. Despite it being just syntactical sugar. I wasn't about to list out all the benefits of es6, that would take several entire blog posts.
- jeremiep 11y ago
  I would rather see ES6 with no class support whatsoever and having people learn to code without them instead of adding features to satisfy the lowest common denominator. I've used classes in CoffeeScript and regretted it every single time. Once your web project starts to grow in scale classes quickly become your first pain point. Especially given how functional JS libraries have become nowadays.
  - warfangle 11y ago
    Composition over inheritance wins, so hard. (edit: downvote for a typically well-thought-of idiom, especially with regard to a language like js? .. if you disagree, why not talk about it?)
    - Touche 11y ago
      Classes are unavoidable in JavaScript if you care about performance. Recreating redundant functions inside a closure in performance critical code is a sure way to have slow apps.
      - jeremiep 11y ago
        Creating an object and creating a closure both need to allocate memory in the VM, but the closure doesn't need to expose its internals the way an object does and therefore can be further optimized by the runtime. If you need to write performance critical JavaScript, then allocating new objects will be just as slow as creating new closures. In either cases you should allocate them ahead of time and then closures are still the clear winner.
        deleted 11y ago
        [deleted]
        warfangle 11y ago
        > Creating an object and creating a closure both need to allocate memory in the VM, but the closure doesn't need to expose its internals the way an object does and therefore can be further optimized by the runtime. Actually... creating an object instance via a constructor lets the runtime use an internal class, which improves performance (as long as you don't modify its properties post-construction). This is a well-known aspect of V8 performance.
        jeremiep 11y ago
        Even with an internal class you're still doing lookups for properties. A closure can instead use local variables which are accessed by index. Why do you think its good practice to pull properties out of objects and into local variables before a tight loop?
        Touche 11y ago
        > If you need to write performance critical JavaScript, then allocating new objects will be just as slow as creating new closures. No, it won't. This code: function createThing() { return { doSomething: function(){} }; } Performs much worse (at scale) than this code: new Thing(); And it consumes a lot more memory since Thing.prototype.doSomething is 1 function in memory and the former is N functions.

Cshelton 11y ago

Yes, but people coming from java or c# or something will like it. Despite it being just syntactical sugar. I wasn't about to list out all the benefits of es6, that would take several entire blog posts.

jeremiep 11y ago
I would rather see ES6 with no class support whatsoever and having people learn to code without them instead of adding features to satisfy the lowest common denominator. I've used classes in CoffeeScript and regretted it every single time. Once your web project starts to grow in scale classes quickly become your first pain point. Especially given how functional JS libraries have become nowadays.
- warfangle 11y ago
  Composition over inheritance wins, so hard. (edit: downvote for a typically well-thought-of idiom, especially with regard to a language like js? .. if you disagree, why not talk about it?)
  - Touche 11y ago
    Classes are unavoidable in JavaScript if you care about performance. Recreating redundant functions inside a closure in performance critical code is a sure way to have slow apps.
    - jeremiep 11y ago
      Creating an object and creating a closure both need to allocate memory in the VM, but the closure doesn't need to expose its internals the way an object does and therefore can be further optimized by the runtime. If you need to write performance critical JavaScript, then allocating new objects will be just as slow as creating new closures. In either cases you should allocate them ahead of time and then closures are still the clear winner.
      - deleted 11y ago
        [deleted]
      - warfangle 11y ago
        > Creating an object and creating a closure both need to allocate memory in the VM, but the closure doesn't need to expose its internals the way an object does and therefore can be further optimized by the runtime. Actually... creating an object instance via a constructor lets the runtime use an internal class, which improves performance (as long as you don't modify its properties post-construction). This is a well-known aspect of V8 performance.
        jeremiep 11y ago
        Even with an internal class you're still doing lookups for properties. A closure can instead use local variables which are accessed by index. Why do you think its good practice to pull properties out of objects and into local variables before a tight loop?
      - Touche 11y ago
        > If you need to write performance critical JavaScript, then allocating new objects will be just as slow as creating new closures. No, it won't. This code: function createThing() { return { doSomething: function(){} }; } Performs much worse (at scale) than this code: new Thing(); And it consumes a lot more memory since Thing.prototype.doSomething is 1 function in memory and the former is N functions.