Why does it exist at all?
We're already using immutable values in Javascript thanks to React. This takes the form of manually cloning objects before mutating them, or using immutable-helpers, or immutable.js. This lets us reason about the data flow easily, and more importantly, allows React's shouldComponentUpdate do dirty check using fast reference equality.
Functional programming - in FP languages, all functions are curried by default. So you don't need the awkward `bind` function to use it. Add extremely light weight function definition syntax and tail-call optimizations, and we have a language with first-class functions.
Types - The adoption of Flow and TypeScript has brought to light a pent up need for some structure and sanity when writing large codebases. ReasonML is OCaml, and it has a very powerful and sound type system.
Since Immutability, functional programming, and Hindley-Milner type systems are becoming ever more necessary to build complex front-ends, it makes a lot of sense to simply use a language that was designed for it. OCaml in its current form has been around for more than 20 years, and the research and other languages that influenced, is even older. It is a fun beautiful language that lets you focus on the shape and structure of your data front and center.
I'd only add a mention of algebraic data types. I learned enough Elm and Haskell to realize the benefit that they bring to a codebase by allowing an expressive way to define the valid structure of an application's data and state.
Algebraic data types are a basic feature.
the question I had asked that brought up 'algebraic effects' was: does ReasonML have optimized generator implementation which is an essential high level concurrency primitive. I was told generators and other concurrency primitives can be built on top of algebraic effects.
Btw the ReasonML you're talking about is still just a syntax transform; you're really asking whether OCaml/BuckleScript has these implementations. There's no generators; but I do believe they can be built on top of algebraic effects.
Regarding jargons: you don't have to worry about that =). Though I think what's more crucial is the way the jargons are conveyed, rather than the meanings themselves. I work in the ReactJS community, and there's basically as many jargons (some of which I myself don't quite understand...) as in FP, yet people seem fine with them. We're still not gonna go "monad this monad that" like you feared. Though if the JS community starts picking up terms like monads in the future thanks to Reason, then all the better.
Just noting that types have been around in programming longer than 2012 (when TypeScript first came out).
It's possible for someone to be an expert in both JavaScript and OCaml. Or any language. The JavaScript language is both approachable and in wide use, attracting not only novices, but experts from many domains.
It seems silly to assume the "JavaScript community" is no more than its lowest common denominator of novice programmers, jumping on bandwagons without any historical context. People are jumping on bandwagons, sure. But every bandwagon needs a driver, who by necessity must be an expert in multiple domains.
The people pushing these trends are not naive to their historical context. They simply see practical benefits worthy of experimentation, and they don't let emotional attachments to their knowledge cloud their judgment.
In that regard, "jumping on the types bandwagon like it's some new discovery" is exactly right, because it's indeed lots of people's first language. But I don't see why this should sound so negative. Newcomers are now introduced to types and they're amazed by them. That's welcomed and we shouldn't feel they're taking away our own shiny toy and tainting them or whatever.
I think it pays to be nice to beginners. Sure, you don't get the usual quality you're looking for in a niche expert language where communications are atomic, on-point, and lossless, but that's _OK_. All in all, things like a better type system, better language semantics and better paradigms are still worth fighting for.
* Facebook is trying to improve the frontend stack out of the goodness of their hearts.
* Facebook is trying to drag their website into the 22nd century by abandoning JavaScript.
* Facebook wants to make the whole world dependent on their software and/or their patent grant.
* The React and Reason teams got drunk together one evening and this is the outcome.
* Yeah! I know I'm pure-hearted at least
* JavaScript will be around for a long time. Our stance is more gradual improvement than world-breaking changes all over the place. I'm still trying to phrase this correctly, because sometimes when Reason gets mentioned, the immediate reaction is "wow they're gonna rewrite everything again, kids...". Our interop story is pretty damn good. Please check it out!
* See ReasonReact's license =)
* The more successful Reason is, the less we'll drink. Kidding
Our discord channel is at discord.gg/reasonml. I think we're a bunch of pragmatic and nice folks. It'll take time for people to understand our stance, but blog posts like these really help showing what we're doing.
Some things I feel are an improvement over Javascript + Flow or Typescript are:
- immutable data structures built into the language (and more conventionally used)
- real pattern matching on types, 'variant' types (like enums in Rust)
- better dead code elimination (helps to keep browser payload size down)
- you can use expressions everywhere (allowing more flexible code style than Javascript)
- currying/partial evaluation
- under the hood it's really just OCaml, which has benefitted from many years of development and improvement
I am not a react developer but I have heard that one of the common complaints about React is ... that it's not Elm, or in more explicit terms, in case you don't know anything about Elm, ... that it's very easy to write code that will break if you poke it the wrong way.
In a static typed language such as Elm (or Reason, based on skimming briefly)... when you get input that can mutate the state of the program, it comes in the form of a message. The messages are typed, so you know what values to expect.
If you write a switch/case statement that handles a message type, the compiler will balk at you if you change the values that the message type can have, without updating the case statements that operate on that type to cover them all.
tl;dr: because runtime errors are a b
I group Reason (Ocaml/Bucklescript) and Fable (F#) together because F# is OCaml's sibling language on .Net. They're very similar. The two projects have similar philosophies, specifically to bring their ML variant to the javascript ecosystem in a module-by-module mixed-language fashion instead of having the language be its own island in the browser. Neither has a particularly large community but the Reason guys have been doing a better marketing push this month, at least from my perspective.
I'm not familiar with the latest ECMA and standards updates and I suppose I don't really know what modern JS actually looks like, but the example on this page[1] doesn't look like syntactically valid JavaScript to me.
If you write code that has to be compiled before it turns into JavaScript, there's another benefit though... it's that you can never accidentally promote code to a server that hasn't already been vetted by the type-checker!
Or, even run it locally! You are guaranteed that the type checker has been run before the code hits a runtime environment.
Looking at Flow, I'm seeing there's a tool `flow` that you run any time you want to check the types. I think there's a background process way to run flow, that mitigates this issue somewhat... but if Flow is in fact implemented to always be syntactically valid JavaScript, that could be a bad thing.
No way. Even in its most basic, untyped form the React model simplifies things all the way down your app pipeline. Errors that used to be common tend to naturally vanish over time.
We have some fairly sophisticated JavaScript that is part of our app, but we haven't drank any of the modern JS kool-aid yet, the only validation we're really using is a suite of feature tests written with Cucumber and Selenium/Chromedriver.
So if you have some JavaScript and it is functionally important to a feature that you've tested, it will show on the CI result if it's broken... but if there's a JavaScript error during the test that didn't stomp on the behavior tested by the feature, you'd never find out about it unless you happen to be watching the Inspector console at the time.