Show HN: C#-to-JavaScript compiler powered by Microsoft Roslyn

by DuoCode • 12 years ago

155 96 12 years ago

Osiris2• 12 years ago

I'm curious how this handles the very common case of passing functions as parameters in JavaScript. I know it's possible in C# but it's much more difficult to do. JavaScript is a much more functional language than C# and the design patterns are quite different.

grokys2• 12 years ago

In what way is it more difficult in C#? C# has lambda syntax:

   obj.Function(() => { ... });

recursive• 12 years ago

I'm curious why you think it's more difficult. Aside from static vs dynamic typing issues, it's pretty much identical.

rjbwork2• 12 years ago

C#:

    Func<string> blah = () => "im a function";

JavaScript:

    var blah = function(){ return "im a function"};

Not only is it not harder, it's more terse in C#.

grokys2• 12 years ago

That can be made even simpler in C#:

var blah = () => "im a function";

Osiris2• 12 years ago

My C# skills must be out of date. Previously you had to use delegates and it was pretty cumbersome.

jaked89• 12 years ago

Even with delegates, C#'s version is pretty much equivalent to JS's:

JavaScript:

  var blah = function(){ return "im a function"};

C# 3.0:

  var blah = delegate { return "im a function"; };

C# 2.0:

  Func<string> blah = delegate { return "im a function"; };

WhitneyLand• 12 years ago

Well done. I like it but I'm not sure what my use case would be. I mean, if I wanted a cross compile language upgrade how do you decide between something like this and ES6?

Also, if there any language left that doesn't convert to JS?

Sanddancer2• 12 years ago

A quick googling shows that people are still having some problems with fortran to javascript, as there's a bit of a dance between toolchains that needs done there. However, the best bet for if you wanna keep people from turning your code to javascript seems to be PL/I. Finding even less there for tools to convert it to javascript.

mwcampbell• 12 years ago

Can C# classes compiled in this way be exposed to JS, so the main program can be in JS with libraries compiled from C#? Or is it assumed that the main program is in C#?

Scarbutt4• 12 years ago

So is this a Microsoft project? they don't directly say it, but they try to make it sound as it is:

"DuoCode is an alternative compiler, powered by Microsoft® Roslyn, and integrated in Visual Studio."

slg2• 12 years ago

Roslyn[1] is open source, so nothing that is being listed there implies Microsoft is behind this project.

[1] https://github.com/dotnet/roslyn

Scarbutt4• 12 years ago

for me, the key in that sentence is "integrated in Visual Studio", implying it comes or will come bundled with Visual Studio, English is not my first language so maybe I'm misinterpreting this.

Someone1234• 12 years ago

I do not believe so looking at the WhoIs:

References this company: www.eternix.co.il

bunderbunder• 12 years ago

Probably not. Roslyn is kind of a buzzword in the .NET space, especially since they open-sourced it early last year.

rdwallis3• 12 years ago

In gwt, reflection isn't supported because it makes it hard for the compiler to do dead code elimination.

Supporting reflection might make it difficult to reduce the compile size of the javascript code in the future.

Or does c# reflection work differently from java?

Looks great by the way.

SigmundA• 12 years ago

C# / .Net will have the same issue, but when they developed native compilation for windows phone apps they added a concept of a runtime definition file that lets you control how much needs to be retained for reflection: http://msdn.microsoft.com/en-us/library/dn600639%28v=vs.110%...

The native compilation technology is moving over to normal .Net and I would imagine the runtime definition file could be used for javascript transpiling tree-shaking as well.

rdwallis3• 12 years ago

Thanks on first glance that looks like a much better solution than gwts' generators.

JamesXNelson4• 12 years ago

I actually have fully functioning reflection in GWT in a branch of my own, and will be getting it merged to master shortly after the GWT.create conference.

https://github.com/WeTheInternet/xapi/tree/master/gwt/gwt-re...

If you want to support complete reflection across the board it greatly swells compile size, but I have made it so you can be selective about what supports reflection, in order to avoid code bloat.

rdwallis3• 12 years ago

Wow the whole xapi project is great, thanks for the link.

How much do the threads actually work yet? How slow are they?

urvader• 12 years ago

    // JavaScript code generated by DuoCode
    GetBestMove = function(board, player, winner)

That line will garbage the global scope..

matchu2• 12 years ago

The C# function is global, so the compiled Javascript function is global. Feels to me like the most correct compilation of the C# code.

(Consider: the C# code has no main function, so, if we hid the GetBestMove definition from the rest of the webpage, it would never get called. The optimal Javascript compilation would be an empty string, and that's clearly not valuable.)

skrebbel• 12 years ago

I'm confused. C# doesn't even support global functions. In your example, it's a static private member of the AI class. Why is it wrong to generate

    var AI = {
        GetBestMove: function(....) { ... },
        ...
    };

Another thing, I had someone tell me once that according to Erik Meijer (of LINQ and Rx fame), years ago, Microsoft tried a C#-to-JS compiler too. It worked, but they had good reasons to drop the project anyway. Did you ever hear about that, do you know Microsoft's reasons for doing TypeScript instead? Are they still valid?

Touche• 12 years ago

Not sure what you mean, you mean it will cause the global scope to be garbage collected, because it will not. It will cause GetBestMove to never be garbage collected though, which is probably ok.

igl2• 12 years ago

He probably meant to put stuff into the global scope is garbage. As in a 'bad idea', not GC.

danbruc• 12 years ago

There is also Script# [1] which unfortunately seems to be no longer maintained. Even the domain of the homepage expired at the end of 2014. I used it for a couple of toy projects and it worked pretty well.

[1] https://github.com/nikhilk/scriptsharp

kingmanaz• 12 years ago

IMHO, Transpilers will likely be the future of web development, with javascript evolving into an intermediate language which other languages are compiled to. Projects like this or gopherjs are a taste of what's to come.

JustSomeNobody• 12 years ago

As long as we're doing predictions, here's mine:

All the cool kids will finally stop trying to push everything to the browser, move some of that back to the server, and become completely content with what Javascript has to offer.

JamesXNelson4• 12 years ago

Why spend cycles doing work on the shared resource (the server), when you can leverage the (hopefully) millions of CPUs used by clients?

Smart clients reduce server load, and allow increased scale; why pay to make your server turn models into HTML when you can just send the model to the client and let it deal with it however it wishes.

For us at Appian, we use the same models and APIs for web, android and IOS; by having a smart client, the server only has to care about the shared model and executing requested instructions; it doesn't care how the client renders the result, nor should it.

bad_user5• 12 years ago

I love this trend of building compilers for existing languages that target Javascript. Other 2 languages with fully functional Javascript compilers that are worth checking out:

- Scala / Scala.js (http://www.scala-js.org/) and I'm actually using this one for a non-trivial app

- Clojure / ClojureScript (https://github.com/clojure/clojurescript) with some companies using it in production

Both are using Google's Closure compiler to do tree shaking minification and are emitting source maps for the compiled code, so the size of the compiled artifacts is manageable in spite of the huge standard libraries they come with and debugging works well. Normally if you want tree shaking with Google Closure, you have to write code specific for Google Closure, however these compilers are doing that for you.

What you get in comparison with Javascript are saner languages that aren't just a prettified Javascript - completely different type system, awesome standard libraries, packages, saner semantics overall; you get a sane dependency management and build process, by means of their build tools (SBT and Leiningen respectively); you get libraries that are cross-compiled for the JVM and Javascript, so you can do code sharing between the server and the browser and you can use mostly the same tools, like IDEs. For example it's a great experience to use IntelliJ IDEA for targeting the browser with Scala - you get code completion, refactoring, the works.

And yes, the compiled size of the final artifact is a source of worry, but in practice I found to not be an issue and what's awesome is that in the long run it actually saves bandwidth for heavy apps. With Javascript many people tend to avoid using third-party libraries, because every imported library adds to the download size, however with tree shaking you're paying only for what you use. As I mentioned, being a Scala developer I picked up Scala.js and it's completely awesome, in spite of the project being young. Unfortunately these heavier alternatives to Javascript haven't picked up popularity - for some reason people preferred putting lipstick on Javascript and pretend that it's a new language.

I'm happy that compilers for C# are happening as well. My only gripe is that in true .NET fashion I'm not seeing a link to the source, which makes me think that this won't be open-source. Which is a pity.

Scarbutt4• 12 years ago

Don't you still have to link externally to third party libs since 99% of JS libs won't pass through the closure compiler?

bad_user5• 12 years ago

Depends on how you have your project setup. You don't have to pass them through the closure compiler. That's a choice.

igl2• 12 years ago

If you use all features of scala you get at least 16mb pure js boilerplate. Even with dead code elimination you cant get below 100kb with 10 lines of scala. Im not sure if i would call that manageable. Your app might explode into megabytes at one point.

With es6 around the corner and the possibilities those features will provide, i would still bet on pure js. Those precompilers will benefit a great deal too. Symbols and Proxies alone will remove a lot of the hoops they have to go through now.

bad_user5• 12 years ago

It's technically impossible to use all of Scala's features and if you do, you'd pay the same price with equivalent Javascript libraries.

I don't get this argument on the size of a hello world, given that JQuery 1.11 is over 270 KB and most people are just doing simple DOM selection with it, yet they don't complain their hello world comes with 270 KB of stuff they'll never use. Factor in React, Bootstrap, Angular.js or what have you and you can easily reach 1 MB of stuff that's never used for a couple of lines of code.

The app doesn't explode in MB, unless those MB are really needed - which is the fundamental difference between how these work and regular Javascript development. And given that there are some companies using these in production for non-trivial stuff and that nobody has ever reported that, I'm thinking that it doesn't happen.

My current app is currently clocking at 300 KB btw, but I am using the collections from the standard library, I am using a library for reactive streams built by myself, I am using React and I do have some code in it. And personally I find it OK.

j_s2• 12 years ago

List of languages that compile to JavaScript

https://github.com/jashkenas/coffeescript/wiki/list-of-langu...

sremani• 12 years ago

Just want to bring it up, funscript (http://funscript.info/) has been around for a while for F#

Scarbutt4• 12 years ago

Can these compilers really generate "readable and maintainable Javascript" and at the same time generate performant JS? I think this is one of the reasons why languages like Dart and Clojurescript chose the opposite (not generate readable JS).

hougaard• 12 years ago

Hmm.. Wonder if this could breathe life into a Silverlight application that needs a way forward..

dested• 12 years ago

I am a huge fan of Saltarelle [1], which has the save level of support as this project. The only thing it seems to be lacking is proper source mapping abilities, which is currently in a dev branch. It also has many libraries already built, like JQuery or AngularJS. However, full support from Microsoft makes it much more realistic to bring in to a production environment. As a C# developer, this will be something to keep an eye on.

Edit: After reading more, this does not seem to be a Microsoft project.

[1] http://www.saltarelle-compiler.com

j_s2• 12 years ago

SharpKit has a 3+ year head-start selling and supporting their solution (available commercially and under GPL3). I have no doubt they have considered transitioning to Roslyn as well; it is a tough decision for all those who had already built a C# parser. (Note that those using Mono [Saltarelle for sure] will wind up stuck unless they follow along to Roslyn.)

The biggest part of these projects is the re-implementation of the .NET CLR in JavaScript (for example, Saltarelle began life using the Script# runtime with a few tweaks). The more production usage the runtime has seen, the more useful the translation tool becomes!

http://sharpkit.net/

h43k3r• 12 years ago

I don't know how good this is, but I got to know from someone that Microsoft uses a similar thing for their internal uses and their version had a very poor debugging.

bkjelden2• 12 years ago

I would encourage anyone looking at a C# to javascript compiler to check out typescript first.

I've seen projects use a compiler similar to this, and while writing C# sounds great to developers who already know C#, the differences between the C# source and the generated JS make debugging and maintenance difficult.

In my experience typescript provides C# developers much of what they are looking for - type safety, familiar class definitions, etc - while still being very easy to debug.

JeremyMorgan• 12 years ago

Agreed, I wish people would look at TypeScript more in general. It really is a great product that doesn't seem to be catching on very well.

Like many others I think the future of JavaScript is going to be treating it like bytecode. Write your application in whatever language you want for developer convenience and debugging, them push it out to javascript for processing. Seems to be where things are headed.

nawitus• 12 years ago

It seems to be catching on reasonably well: http://blog.javascripting.com/2014/07/28/fastest-growing-new...

judah• 12 years ago

As a former C# guy who moved to the web, I can say with confidence this is true: TypeScript is a great language for building great web apps.

My "Show HN" submission yesterday[0], the web app for helping homeless youth find beds and shelter[1], is written in TypeScript.

[0] https://news.ycombinator.com/item?id=8886588

[1] http://ysnmn.org

TazeTSchnitzel• 12 years ago

TypeScript was made by C# people, too :)

_mtr• 12 years ago

while writing C# sounds great to developers who already know C#, the differences between the C# source and the generated JS make debugging and maintenance difficult.

Isn't this solved with source maps?

DuoCode automatically generates source mappings

jahewson• 12 years ago

Source maps get you line numbers but not live objects - you're still stuck inspecting JS objects.

_random_• 12 years ago

Is there ReSharper or Roslyn for TypeScript? In terms of powerful AND extensible refactoring tools.

solomatov• 12 years ago

ReSharper supports TypeScript. See http://blog.jetbrains.com/dotnet/2014/03/17/more-typescript-...

Also TypeScript is supported by IntelliJ family of IDEs.

novaleaf2• 12 years ago

the new VS 2015 preview uses Roslyn for typescript. honestly I prefer VS 2013 better right now, the VS 2015 preview crashes regularly, plus is missing important extensions (and the Web Essentials plugin for it misses features such as TSLint)

avodonosov• 12 years ago

IMHO the reason for such a compiler is sharing code between client and server. From that standpoint your advice is reasonable for C# programmers only if they are ready to abandon C# altogether and switch to node.js on server.

bkjelden2• 12 years ago

That's true - if you have some sort of business logic you want to run on both client and server, this or Script# could be very useful.

But if you're looking to write C# in the browser because you love C# and have heard JS is terrible (a BIG factor I've seen used when pushing tools like this), I'd look at typescript first.

jtwebman6• 12 years ago

I don't find writing JavaScript to be that hard. I don't get all of these compilers like this one, CoffeeScript, and TypeScript. Are people really that lazy that they can't spend the couple days it takes to learn the syntax and gotchas of JavaScript?

justathrow2k2• 12 years ago

I don't think laziness or a lack of desire to learn java script is the driving force for these projects. Rather, its simply for people who prefer a facade of strong types over their java script.

jtwebman6• 12 years ago

What do strong types get you? Being I write a bunch of C# at work and almost all JavaScript at home I find types very limiting, so I still don't get why?

px19992• 12 years ago

I'm working with a singlepage webapp that consists of ~1.5MLOC serverside(+other) and an additional ~100KLOC of javascript (not including libraries).

Refactoring and maintaining consistency are the two big problems we have with Javascript. It's easy enough to write javascript that works and does what we need it to do. The challenges come in when you start having separate components that need to interoperate.

eshint/jshint etc take you only so far (preventing you from dumping things into the global scope, avoiding typos). AMD etc can take you a bit further with async loading, and give a better [more consistent] pattern for exporting things than saying to devs "just put your stuff in an IIFE". FB Flow looks helpful, but it's trying to solve a difficult problem, and unfortunately doesn't work so well with our code thanks to ONE bad decision made a long time ago to rely on declaration hoisting ("unreachable code" :( ).

Anyways, knowing that your code isn't going to work before you start spinning up the application saves a lot of time.

Knowing that you can rename a method/function and have no undefined errors come out of it is great. Being able to look up usages of a method across the entire codebase is also useful. Eventually if Microsoft decide to spend resources on it, TypeScript might get CodeLens (which is on its own all manner of cool+useful).

Having class syntax means that you don't need to worry about external consumers accessing properties that they shouldn't be (+gets rid of silly conventions like underscore private members/methods).

JS is a great language, and it's powerful, but when you're writing large quantities of stuff, sometimes you need structure. Particularly when it's a large team and there are people of wildly varying experience, ranging from near-zero JS experience to people who have used it for a decade or more.

jtwebman6• 12 years ago

Unit tests fix the changing methods issue as well as making sure it will run when you run it. Types don't save you from that anymore then JSLint would as both can have logic errors.

Browserify can help with breaking your code down into smaller reusable modules for the client side and node you want to make your modules as small as possible? From the sounds of it you fell into the one big huge application that does everything problem instead of breaking it up. The same issues would have happen if you would have done that in any other language.

Varying experience doesn't mean you can give them TypeScript or CoffeeScript and not mess something up. You should still put code reviews and training in place though I do agree JavaScript lets you shoot yourself in the foot much easier.

You can hide variables through closures and sorry not a fan of getters and setters, I feel they are a anti-pattern (http://www.yegor256.com/2014/09/16/getters-and-setters-are-e...).

The one thing that would be nice would be knowing where your code is called. Though if you are using NPM and Browserify then that can be easier as well. I agree though that the tools are not as nice as Visual Studios find callers and the intellisense isn't that good ether but I am willing to trade them for the flexibility of not having to declare types and the simplicity of not having to work around types with generics, interfaces, and casting.

So I think there is structure in Javascript you just have to learn the best ways of implementing it. Yes Javascript makes it a little easier to shoot yourself in the foot but you can still do it with CoffeeScript, TypeScript, or even in C# and Java, we learn from our mistakes. I fell to be successful in Javascript you really need to keep it small and re-factor often but that really is the same in all languages.

xenadu02• 12 years ago

This isn't new. Microsoft had an unofficial project for a while called Script# (script sharp) that did the same thing. I think they rightly decided it was a better idea to support JavaScript directly and come up with a new language designed to target JS from the start (typescript)

elwell• 12 years ago

Cool to see the open-sourcing of Microsoft code already being put to use.

anprak• 12 years ago

Script# has existed for years and heavily used inside Microsoft. Even with that, it was not adopted as a tool for programming JavaScript in Visual Studio. If you need to code JavaScript but not in JavaScript as it exists today, TypeScript is what you should look at.

Please stop these C# to JavaScript compilers. If one needs to program in JavaScript, let them learn and understand JavaScript.

CmonDev2• 12 years ago

Yes! The whole compilation madness must stop. Machine code is good enough for everyone. And if you still need to code in a high-level language, assembly is what you should look at.

nercury• 12 years ago

JavaScript became this "immediate language" that we compile other languages to. Could we instead get rid of it by making PROPER immediate language for the browser?

CmonDev2• 12 years ago

Unfortunately most of the people have been inside the barn long enough to stop noticing the smell, if you know what I mean.

tosh• 12 years ago

If you like the feeling of working with something like C# it is also worth looking into Dart: https://www.dartlang.org/

    * Runs on the client and on the server
    * async/await
    * Well designed stdlib
    * Powerful intellisense support
    * Stream and Future based APIs

Show HN: C#-to-JavaScript compiler powered by Microsoft Roslyn

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