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Comment by flowerlad | Hacker News Reader

I don't get why so many JavaScript developers thing functional is cool. Functional has been around for 30+ years. OOP won against functional because OOP is easier to understand and leads to more maintainable code. These days people are taking a second look at functional because functional avoids state, which makes it easier to write concurrent code with no locks. (This has suddenly become important because Moore's law is coming to an end, and CPUs are adding more cores instead of making cores faster and faster.) But this advantage of functional is not applicable to JavaScript because there are no locks in JavaScript in any case!

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JavaScript is also an extremely bad functional language unless you don't mind ridiculous memory bloat and inefficiency. To be even reasonably efficient you're basically forced to use classes because the primary ergonomic alternative is objects that contain functions that close over lexical scope. This is ridiculously inefficient because functions that would normally have a single instance on the prototype chain are now duplicated for every single object. Modern JavaScript engines can't optimize this without breaking the spec which they obviously won't do. You can resort to just using plain functions and objects that contain nothing but data but this quickly becomes quite ugly without a pipeline operator.

The standard library is also filled with mutating methods and doesn't include proper functional data structures and pure JavaScript implementations of functional data structures, such as immutable.js, are so slow that you might as well just use arrays and objects and repeatedly do shallow copies.

Programs that stress functional purity in JavaScript are becoming hard to meaningfully benchmark because instead of having a few hotspots absolutely everything is incredibly inefficient and slow. Death by a thousand cuts.

To be fair, JavaScript is also an extremely bad OOP language.

And I’m not complaining about its prototypical inheritance either (I actually like it), but the fact that it tries to hide its prototypical nature under a Java like veneer.

It’s hardly JS developers who think functional programming is cool. Scala became huge in the JVM world because of its functional nature. Kotlin includes a lot of functional programming, and Java itself continues to add functional capabilities.

And if you look at the .Net side of things, C# has basically been on a path to look increasingly like F# with every release. And of course, LINQ, one of C#’s most popular features, is little more than a functional subset of C#.

Arguably its backend developers moving to the front end who have been trying to bring functional concepts to front end programming.

Functional programming actually brings some benefits to backend code. To take advantage of the extra cores in a CPU you add threads, but if these threads are continually needing to lock in order to access shared state then concurrency is diminished. The more cores you have, the more threads you have, and then the more you have to lock. Functional style solves this problem by not having mutable state, thus eliminating the need to lock.

But when it comes to JavaScript these benefits don't exist. That's not to say there are no benefits at all to incorporating some functional style into JavaScript code, but wholesale replacement of OOP with functional style is not warranted.

Yeah. I have noticed few instances of badly optimised functional code.

something like

  examples.reduce((accumulator, example) => {

    // logic
   
    return {...accumulator,[example.name]: example.value }

  }, {})

Object spreading and destructuring combined with fancy immutable array methods smell..

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