scala-js/scala-js

Scala.js, the Scala to JavaScript compiler

Anthony Cerruti

@srnb_gitlab

      containerOrNull <- Stream.eval(ce.delay(document.getElementById("container")))
      container <- containerOrNull match {
        case null => Stream.raiseError(new IllegalStateException("No #container found"))
        case found: typings.std.Element => Stream.emit(found)
      }

Sébastien Doeraene

@sjrd

Sure

Anthony Cerruti

@srnb_gitlab

:+1: Thank you again :sweat_smile:

aappddeevv

@aappddeevv

I have a bunch of helpers for things like A|Null. Maybe they will be helpful for you. https://github.com/aappddeevv/scalajs-reaction/blob/master/jshelpers/src/main/scala/null.scala. I also encounter UndefOr[A|Null] a lot as well.

Matt Hughes

@matthughes

Trying to upgrade my app to 1.0.0 (from 0.6.33). Can’t figure out why I’m getting this with fastOptJS:

[error] Referring to non-existent method static com.app.client.Main.main([java.lang.String)void
[error]   called from core module module initializers

Tripled checked my Main object:

object Main {
  def main(args: Array[String]): Unit = {

has to be some build setting I messed up but can’t for the life of me figure out what.

Matt Hughes

@matthughes

If I make no changes to that file, but delete all other source files in my project, fastOptJS succeeds.

Anthony Cerruti

@srnb_gitlab

1.1.0 is the latest ScalaJS version, maybe that fixed something wrt linking? but I'm not sure, just a [i forget the idiom]

Matt Hughes

@matthughes

It clearly doesn’t like something in my app but error message isn’t pointing it out. I’m on 1.1 but can’t downgrade due to other libraries that published for 1.1

Matt Hughes

@matthughes

It’s getting weirder:

import org.scalajs.dom
// Links with this import commented out, fails with it uncommented
// import scala.scalajs.js._

object Main {

  def main(args: Array[String]): Unit = {
    val root = dom.document.getElementById("root")

    println(s"Hello $root")

    ()
  }
}

Anthony Cerruti

@srnb_gitlab

Oh yeah, usually you don't import js._, you import js and use js.Dynamic.global or js.Object or etc

That may be why it fails with that import: It sees Array[String] and thinks js.Array[js.String] which isn't a valid main

Matt Hughes

@matthughes

oh. my. gosh. wow thanks! It worked before because 0.6 didn’t take args: Array[String].

Anthony Cerruti

@srnb_gitlab

:+1: glad you got it figured out!

Mark Tomko

@mtomko

We have a library in our code that includes a class that does (eg, DNA) sequence alignment. To do this, it uses a bunch of scoring matrices that are defined in text files (they're in the public domain, and our code parses them). In the JVM version of our library, we bundle the the matrix files in the jar by putting them in src/main/resources, and we load them using the classloader. We're trying to cross compile this library with scala JS and we'd like to figure out how we can write code targeting the JS runtime that can load them.

Is there a way to do this? Currently the code compiles but the tests fail with linking problems like: Referring to non-existent method java.lang.Class.getResourceAsStream(java.lang.String)java.io.InputStream

Mark Tomko

@mtomko

Obviously classpath makes sense as something that doesn't exist in the JS environment but I'm curious if there's an alternative for reading out resources

Roman Janusz

@ghik

Where are you going to run that library? Browser, Node?

Mark Tomko

@mtomko

Probably in the browser

Roman Janusz

@ghik

Then you'll have to decide how are you going to load these files in the browser, e.g. separately from external URL?

You might want to look at various bundling options that webpack gives you

Mark Tomko

@mtomko

okay. so there's no way to have the scalajs compiler encode them somehow in the JS resource that it produces?

Roman Janusz

@ghik

There may be but webpack can do that for you better

Mark Tomko

@mtomko

I guess we were hoping for a common way of loading these between the JS and JVM code; if we need to use some other tool for the JS verison, we might as well split the associated classes up

unless I am not understanding you properly

Roman Janusz

@ghik

JS simply has no concept of files or classpath so you cannot avoid having two separate implementations for loading these resources

I guess the most common ground would be URLs - on JVM they could point to classpath resources while in JS they would be actual internet URLs

I guess you're asking about some potential mechanism in the Scala.js linker which emulates classpath resources but there's not such thing AFAIK

Mark Tomko

@mtomko

Yes, I guess that's what I was hoping for, but it looks like we'll have to tackle it some other way.

Roman Janusz

@ghik

webpack may really be your friend, e.g. https://webpack.js.org/loaders/file-loader/

Mark Tomko

@mtomko

I'll take a look at it, thanks

Roman Janusz

@ghik

Scala.js integrates with webpack via scalajs-bundler

aappddeevv

@aappddeevv

@mtomko If you are using webpack, then one option is webpack module aliases. You can define an alias to "Resources" that points to your project's resources folder. Then you can import the resources, whatever they are, using @JSImport("Resources/myresourcefile.conf", JSImport.Default) or whatever import makes sense for you. You can also skip the alias and add the webpack loader directly to the JSImport but that's a bit messy.

The new val/def import capabilities are real useful here if you are using 1.1

Mark Tomko

@mtomko

thanks, i'll check that out

acse-fk4517

@acse-fk4517

Hi, is there a way to compile and run scala.js code from Scala running on the JVM? I have an app written on the JVM, but I would like to take advantage of the extensive javascript charting libraries out there

Sébastien Doeraene

@sjrd

Do you really want to compile the Scala.js code on the fly doing your JVM program's execution?

Or are you satisfied with compiling the Scala.js code ahead of time, and the only thing you want is call the already compiled JavaScript code from the JVM?

For the former, you'll need to invoke scalac with the Scala.js compiler plugin, then call the Scala.js linker, all from your JVM app. Look at how ScalaFiddle does it for inspiration.

For the latter, you can just spawn a node process and communicate with it via standard in/out or TCP. You may find the NodeJSEnv class useful for that purpose.

acse-fk4517

@acse-fk4517

@sjrd thank you - I will take a look at those

acse-fk4517

@acse-fk4517

@sjrd Essentially I run some simulations and the data is output in some format. I looked at the JVM plotting options and they are poor compared to whats available in Javascript. So I guess what I wanted to do was have a well integrated plotting package that accompanies the main simulation library which sits on the JVM.

Anthony Cerruti

@srnb_gitlab

Did you see EvilPlot by any chance? @acse-fk4517 It's working towards being able to do what other languages can do

https://github.com/cibotech/evilplot

acse-fk4517

@acse-fk4517

thanks @srnb_gitlab , however I couldn't get the basic example to render on my macbook. The Java icon pops up but nothing shows up. Another one I looked at is Xcharts which seems promising

Anthony Cerruti

@srnb_gitlab

You should be able to render it to an image instead of a Java Window

You have to extend https://cibotech.github.io/evilplot/scaladoc/jvm/com/cibo/evilplot/geometry/RenderContext.html

And implement the draw operations

acse-fk4517

@acse-fk4517

thanks @srnb_gitlab

aappddeevv

@aappddeevv

@acse-fk4517 You could also use graal, if that type of jvm works for you.

acse-fk4517

@acse-fk4517

@aappddeevv thanks!

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