Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Facebook Launches Flow, Static Type Checker for JavaScript

code.prod.facebook.com

Post reply on HN
Print view View original

141–150 of 282 posts

Re: Facebook Launches Flow, Static Type Checker for JavaScript

#141

Post by aliakhtar »

krapp wrote: post #131
aliakhtar wrote: post #126

Earlier quoted context omitted.

All the language features of java: generics, inheritance, type safety, interfaces, and soon to come: lambdas and other Java 8 features, are all supported. Plus your code is organized in java packages. So, I'm not sure you've ever tried GWT. Things like multi threading which aren't possible in javascript aren't supported, but a lot of the JRE which is used in most code, does come out of the box. Its a huge improvement…

Those are features of the IDE, and of Java, certainly. But type safety doesn't really exist in javascript. Structures like interfaces and classes don't really exist. Inheritance is different. Scope is different. What you have is a javascript framework which emulates the behavior of Java to the degree that javascript permits, but can't really implement it. I'm not saying it isn't a useful tool, or that the javascript…

>type safety doesn't really exist in javascript. Structures like interfaces and classes don't really exist. Inheritance is different. Scope is different.

You are not coding in javascript. You are coding in java, and the code is then converted into highly efficient javascript by a compiler.

> What you have is a javascript framework which emulates the behavior of Java to the degree that javascript permits, but can't really implement it.

Absolutely not. You are actually coding in java, and its then compiled to javascript. Have you ever used GWT?

Re: Facebook Launches Flow, Static Type Checker for JavaScript

#142

Post by callum85 »

Shizka wrote: post #132
cdelsolar wrote: post #129

Earlier quoted context omitted.

Read the Good Parts of Javascript and get a JS linter. Javascript is a fine language if you do this.

I've had the exact same concerns as the person you replied to. I just want to make sure since the title differs from the one you stated. Is this the book you were talking about: http://www.amazon.com/JavaScript-Good-Parts-Douglas-Crockfor... And how/why did the book improve your opinion about the language?

It's an opinionated book that sets out a subset of JavaScript that you should use, avoiding all the 'bad parts'. This subset is what tools like JSLint and JSHint were designed to promote - they flag you up if you use a bad part. It's a seminal work. These days I find some of its rules a little dogmatic (for instance I like the 'new' keyword now), but I'm glad I went through a phase of sticking to it relgiously for a while. It taught me to stop bitching about the weird parts, just avoid them instead. And when you do this, you end up loving the language and making cool shit with it. Which is a good situation to be in, because it's the most widely distributed runtime in the world.

Re: Facebook Launches Flow, Static Type Checker for JavaScript

#143

Post by aikah »

cdelsolar wrote: post #129
kulkarnic wrote: post #127

Earlier quoted context omitted.

Is this a serious post, or are you being sarcastic? I honestly can't tell. JS the language of the future? Why? It has probably the worst gotchas of any language I've coded in, it's verbose, and weird scoping. Nor is it especially nice to optimize for/with. I can certainly see being stuck with Javascript (just like we're stuck with the x86 instruction set even if simpler alternatives exist), but I'm not sure it's some…

Read the Good Parts of Javascript and get a JS linter. Javascript is a fine language if you do this.

> Javascript is a fine language if you do this.

No,it's not fine, it's a horrible language,with a few good features that saves it from being a catastrophy.hence "Good Parts".

Or we wouldnt be here talking about Flow,Typescript or others if the language was "fine". JS was clearly not designed for what we are making out of it today.

But since there is no way around Javascript in webdev,good or bad,it doesnt even matter.It exists.TC39 isnt going to fix types,so types are fixed in userland.hence "Flow".

Re: Facebook Launches Flow, Static Type Checker for JavaScript

#144

Post by [deleted] »

ep103 wrote: post #68

This looks like such a better step in the right direction than than the types of tools MS and Google have been putting out. Dynamically discerning the underlying code, and allowing optional type annotation works _with_ javascript, as opposed to attempting to turn js into a completely different (and weakened) language. That said, I am curious what solutions this solves that isn't already solved by enforcing good code…

[deleted]

Re: Facebook Launches Flow, Static Type Checker for JavaScript

#145

Post by pedrocr »

cdelsolar wrote: post #129
kulkarnic wrote: post #127

Earlier quoted context omitted.

Is this a serious post, or are you being sarcastic? I honestly can't tell. JS the language of the future? Why? It has probably the worst gotchas of any language I've coded in, it's verbose, and weird scoping. Nor is it especially nice to optimize for/with. I can certainly see being stuck with Javascript (just like we're stuck with the x86 instruction set even if simpler alternatives exist), but I'm not sure it's some…

Read the Good Parts of Javascript and get a JS linter. Javascript is a fine language if you do this.

This is the standard advice in these threads. I've found the book quite short of that goal. It has a few patterns to make the stranger parts a bit more bearable but real world JS still fails in all sorts of non-obvious ways unless you're very familiar with it. I hope the newer versions JS versions have gotten better

It used to be that building a competent web app was something you could do in a number of different languages, these days you really need to know JS or one of it's skins and it's made developing for the web much less friendly to people that don't do it every day.

Re: Facebook Launches Flow, Static Type Checker for JavaScript

#146

Post by lobster_johnson »

kulkarnic wrote: post #127
DigitalSea wrote: post #39

What a great tool. Facebook are absolutely killing with the last year or so with all of their open source contributions and releases. First HHVM, Haxl, React.js (amongst other things) and now Flow, this is fantastic. I am really liking how companies like Facebook & Google are concentrating their efforts on the web language of the future: Javascript. The support for JSX alone is a MASSIVE feature (expected given React…

Is this a serious post, or are you being sarcastic? I honestly can't tell. JS the language of the future? Why? It has probably the worst gotchas of any language I've coded in, it's verbose, and weird scoping. Nor is it especially nice to optimize for/with. I can certainly see being stuck with Javascript (just like we're stuck with the x86 instruction set even if simpler alternatives exist), but I'm not sure it's some…

JavaScript is changing rapidly. ES6 and TypeScript are fixing the warts and adding much-needed features. And you can use those features today, thanks to projects like Traceur, 6to5, TypeScript and Flow.

If you factor in all these improvements, and the fact that it runs brilliantly on the server, it's a vastly different situation than just a few years ago.

Re: Facebook Launches Flow, Static Type Checker for JavaScript

#147

Post by dreamweapon »

DigitalSea wrote: post #39

What a great tool. Facebook are absolutely killing with the last year or so with all of their open source contributions and releases. First HHVM, Haxl, React.js (amongst other things) and now Flow, this is fantastic. I am really liking how companies like Facebook & Google are concentrating their efforts on the web language of the future: Javascript. The support for JSX alone is a MASSIVE feature (expected given React…

I am really liking how companies like Facebook & Google are concentrating their efforts on the web language of the future: Javascript.

"...on the web language of the past, which we are unfortunately stuck with for the foreseeable future: JavaScript" might have been a better summation of the current (rather dismal) state of affairs with regard to web scripting.

Re: Facebook Launches Flow, Static Type Checker for JavaScript

#148

Post by peq »

inglor wrote: post #44
slashnull wrote: post #31

At last! This all seem extremely cool. I went straight from hacking Scala and Haskell as a hobbyist to doing (mostly) front-end JS job, and I've always found that my code, and a lot of good libraries I read, naturally emulate something close to Hindley-Milner typing, by using objects as tuples/records and arrays as (hopefully well-typed) lists, as well as the natural flexibility of objects as a poor substitute for Ei…

Strongly typed JS is actually pretty hard - probably not by Haskell and Scala standards - but if you take promises for example the signature of `then` is: Promise -> ((A -> (Promise | B)),(E -> (Promise | C))) -> Promise That is - a promise's then - takes the promise (as this) and executes either a `.then` fulfillment handler or a catch handler. If the `fulfill` handler executes the value is unwrapped and either a ne…

I think sometimes types lead to simpler designs. For example why can't "then" just have the following type:

Promise A E -> (A -> A') -> (E -> E') -> Promise A' E'

That would eliminate some strange corner cases and make it easier to explain the function. The special cases could just get their own functions. Real algebraic data types would probably eliminate the need for E entirely and make it even simpler.

Re: Facebook Launches Flow, Static Type Checker for JavaScript

#149

Post by lpw25 »

nevir wrote: post #125
mjackson wrote: post #83

This is HUGE! Thanks to everyone at Facebook who worked on this. You guys are awesome. Also: The fact that this is written primarily in OCaml (as opposed to JS) is an excellent example of people choosing the right tool for the job.

IMO OCaml is the wrong tool for the job in this case (even if it is a better language for this sort of tool). JavaScript has a weird ecosystem where it is extremely helpful to have all of your tools in the same language. browser-based IDEs, Node, portability, etc, and just one fewer runtime to juggle. Same reasons why closure is awkward as a Java program.

OCaml has excellent compile-to-JavaScript support. Facebook use this to compile their Hack type-checker for an in-browser IDE. I imagine they do something similar for Flow.
Post reply on HN