scala-js/scala-js

Scala.js, the Scala to JavaScript compiler

Kirill A. Korinsky

@catap

Hey, is it possible to understand in runtime when some object exists? For example org.scalajs.dom.raw.Touch or athing very rare inside org.scalajs.dom?

Sébastien Doeraene

@sjrd

Sure: js.typeOf(js.Dynamic.global.Touch) != "undefined"

Kirill A. Korinsky

@catap

@sjrd thanks, I've played with js.undefined and can't figure it out.

Sébastien Doeraene

@sjrd

See https://www.scala-js.org/doc/interoperability/global-scope.html#practical-tips for more details

Kirill A. Korinsky

@catap

@sjrd following question. Let assume that I'd like to check that const net = require('net'); is possible. How can I do it?

ah, I see

Sébastien Doeraene

@sjrd

Same as in JS: check that require exists, then try/catch.

Kirill A. Korinsky

@catap

js.typeOf(js.Dynamic.global.require) != "undefined"

Eric K Richardson

@ekrich

@sjrd Any chance that regex code will be useful for Scala Native?

Sébastien Doeraene

@sjrd

Absolutely not. It's a compiler from Java regex to JS regex. It's only useful if you have a JS regex engine to begin with.

William Narmontas

@ScalaWilliam

Hi all, I could not find the right way to do this - how do you do this in Scala.js?

import 'codemirror/mode/clike/clike';

It's a side-effecting import

Sébastien Doeraene

@sjrd

With an @JSImport("codemirror/mode/clike/clike", JSImport.Namespace) object Foo extends js.Any, and then you make sure that actually reach Foo, e.g., by putting it in your main method, or any other code that will run in all the cases where you need those side effects to have been executed.

William Narmontas

@ScalaWilliam

thank you @sjrd !

Mat Fournier

@mat4nier_twitter

:wave: what's everyone's preferred way to do websockets in scalajs? Curious what my options are floating around.

Antoine Doeraene

@sherpal

It really depends in what context you want to use them. But for me, since I'm working with the Laminar framework, I like to wrap the websockets inside "event stream" and "observers". (Usually by adding an automatic layer with decoders and encoders, such as, for example, circe (when speed is not an issue but debugging is) or boopickle (when speed is an issue and debugging is not)).

Brandon Elam Barker

@bbarker

is it possible to use scala-js-dom from Scala 3 by some means, currently?

Mat Fournier

@mat4nier_twitter

@sherpal thanks. Already using laminar so I'll go look into that.

1 reply

Sakib Hadžiavdić

@sake92

@bbarker yes with ("org.scala-js" %%% "scalajs-dom" % "1.1.0").cross(CrossVersion.for3Use2_13)

Kirill A. Korinsky

@catap

@sjrd another fast and wired question. How can I use js.FunctionN in scala 2.11? Naive approcach fails with scalac error: The argument types of an anonymous function must be fully known. (SLS 8.5)

new js.Function1[js.UndefOr[js.Error], Unit] {...} fails with A non-native JS class cannot declare a concrete method named apply without @JSName

Sébastien Doeraene

@sjrd

You have to explicitly write the parameter types of your anonymous function, that's all.

So not (x, y) => x + y but (x: Int, y: Int) => x + y

Or use the -Xexperimental option of scalac 2.11, if you feel adventurous.

Kirill A. Korinsky

@catap

got it, thanks

Hanns Holger Rutz

@Sciss

which one is more effective to transfer via XHR and decompress in sjs, jar or zip?

Sébastien Doeraene

@sjrd

@Sciss Hum, I don't think I understand the question.

jar and zip are exactly the same thing. You can rename a .jar into a .zip and you'll be able to open it.

Hanns Holger Rutz

@Sciss

I thought they were "more or less" the same thing, didn't know they are exactly the same. So in SJS I would just use java.util.JarInputStream, and that would work? Or is there a better and more direct mapping to underlying JavaScript API for that?

Sébastien Doeraene

@sjrd

That would work if JarInputStream were implemented at all, but that's not the case (at least not in the core repo).

Hanns Holger Rutz

@Sciss

Ok. So I would have to use JS API to decompress?

Sébastien Doeraene

@sjrd

If you want to read a zip/jar file in Scala.js, consider using a JS library like jszip.

Hanns Holger Rutz

@Sciss

Got it, thanks

Brandon Elam Barker

@bbarker

thanks @sake92 !

Hanns Holger Rutz

@Sciss

why would this happen in fastOptJS but not fullOptJS:

org.scalajs.linker.runtime.UndefinedBehaviorError: java.lang.ClassCastException: 0.019759721189251594 is not an instance of java.lang.Integer

Sébastien Doeraene

@sjrd

@Sciss Because that's literally the role of fastOpt: https://www.scala-js.org/doc/semantics.html#undefined-behaviors

Sakib Hadžiavdić

@sake92

Would it be possible to warn on %% dependencies in ScalaJS-only projects?

It happened to me a few times due to copy-paste :smile:

Andriy Plokhotnyuk

@plokhotnyuk

@sake92 Compile-time only dependencies work fine with %% or % for Scala.js projects.

2 replies

Sébastien Doeraene

@sjrd

Tomorrow at 4:30 CEST, discover my take on the best features of Scala 3 for Scala.js users:

https://twitter.com/47deg/status/1384202888277233669?s=19

It will happen at the following YouTube link, and I'll be in the chat section to answer comments: https://youtu.be/llGtGd4qux0

Anton Sviridov

@velvetbaldmime:matrix.org

[m]

That was great, thanks @sjrd !

The opaque pattern is very cool - and probably would have a good effect on the size of the generated code with all those classes removed?

Sébastien Doeraene

@sjrd

Thanks :)

The generated code will be exactly the same. traits that extend js.Any have no footprint JS.

August Nagro

@AugustNagro

Great talk Sebastien, learned some new things. I'm a big fan of the anonymous class inference for config objects.. the 'two lookup' problem is one of my biggest annoyances with using any compile-to-js language.

Sébastien Doeraene

@sjrd

Thanks :)

Andrew Adams

@adamsar

Hey I just checked out the video, learned some good stuff thanks. I also felt like I got a personal shout out with the | syntax gitter part ;)

Sébastien Doeraene

@sjrd

The video was recorded a month ago. It was not targeted at a single example. It has been the most common question here for the past 5 years.

Andrew Adams

@adamsar

Hopefully will no longer be the top question soon!

Sébastien Doeraene

@sjrd

Yup ;)

Where communities thrive

People

Repo info

Activity