KSUG ScalaJS: Yet another what… ? It’s tempting to write your whole web application in one and only programming language, especially when this is yours language-of-choice. That’s the reason why Node.js got so much traction in the last years - JavaScript is the part of the web stack which will stay there, whether we like it or not. In the world of languages compiled/transpiled to it, there is ScalaJS that is trying to keep its head above water and gain some popularity. Let’s take a look and try to evaluate if it’s worth our time to try it.

1. Scala.js
Yet Another What... ?
Created by /Artur Skowroński @arturskowronski

2. #JavascriptEverywhere

3. There are a problems with big
apps in Javascript

4. We have transpiled languages

8. We have compiled languages

9. Google Web Toolkit

10. Opal (Rb 2 JS)

11. CobolScript

12. Brainfuck.js

13. Scala.js

14. Said to be production ready

15. Functional JavaScript is getting
popularity

19. Functional Reactive
Programming

20. Example 1

21. object ScalaJSExample extends js.JSApp{
def main() = {
var x = 0
while(x < 999){
x = x + "2".toInt
}
println(x)
}
}

22. ScalaJS.c.Lexample_ScalaJSExample$.prototype.main__V = (function() {
var x = 0;
while ((x < 999)) {
var jsx$1 = x;
var this$2 = new ScalaJS.c.sci_StringOps().init___T("2");
var this$4 = ScalaJS.m.jl_Integer$();
var s = this$2.repr$1;
x = ((jsx$1 + this$4.parseInt__T__I__I(s, 10)) | 0)
};
var x$1 = x;
var this$6 = ScalaJS.m.s_Console$();
var this$7 = this$6.outVar$2;
ScalaJS.as.Ljava_io_PrintStream(this$7.tl$1.get__O()).println__O__V(x$1)
});

23. <script type="text/javascript" src="/oursample-fastopt.js"></script>
<script>
</script>
oursample.ScalaJSExample().main();

24. Example 2

25. object ScalaJSExample extends js.JSApp{
def main() = {}
def exported = {}
def exported2 = {}
}

26. @JSExport

27. object ScalaJSExample extends js.JSApp{
def main() = {}
@JSExport
def exported() = {}
@JSExport
def exported2() = {}
}

28. <script>
oursample.ScalaJSExample().exported();
oursample.ScalaJSExample().exported2();
</script>

29. $.val()?
val is forbidden in Scala

30. @JSName

31. object ScalaJSExample extends js.JSApp{
def main() = {}
@JSExport
def exported() = {}
@JSExport
def exported2() = {}
@JSExport
@JSName('val')
def valueOfObject() = {}
}

32. <script>
oursample.ScalaJSExample().val();
</script>

33. General problem with
Transpiler

34. SBT Plugin

35. addSbtPlugin("org.scala-js" % "sbt-scalajs" % "0.6.0")

36. compile
package
fastOptJS
fullOptJS
run
test

37. compile

38. Initial Compilation: .scala files to .class and .sjsir files

39. package

40. fastOptJs

41. Fast Optimization: .sjsir files to one smallish/fast .js file

42. fullOptJs
Clojure Compiler

43. Full Optimization: .sjsir files to one smaller/faster .js file
Clojure Compiler

44. run

45. object RunMe extends js.JSApp{
def main(): Unit = {
println("Hello World!")
}
}

46. Hello World!

47. Rhino
Node.js
PhantomJs

48. test

49. Source Maps

50. Example 3

51. @JSExport
object Client extends js.JSApp{
@JSExport
def main(container: html.Div) = {
val inputBox = input.render
val outputBox = ul.render
def update() = Ajax.post("/ajax/list", inputBox.value).foreach{ xhr =>
def response = xhr.responseText
(Raw Json Operation)
}
}
}

52. Not Strongly Typed

53. autowire

54. @JSExport
object Client extends js.JSApp{
@JSExport
def main(container: html.Div) = {
val inputBox = input.render
val outputBox = ul.render
def update() = Ajaxer[Api].post("/ajax/list", inputBox.value).foreach{ data =>
(Business Logic on Strongly typed operations)
}
}
}

55. org.scala-js.scalajs-dom
org.lihaoyi.scalatags
com.lihaoyi.utest
com.lihaoyi.uPickle
me.chrons.boopickle
com.lihaoyi.autowire
com.lihaoyi.workbench

56. Quirks

57. Float
println(1.4f)
1.3999999761 58142

58. Lack Of Exception Checking

59. Regular expressions

60. Reflection Support

61. Conclusion

62. Better than
expected :)

63. Strenghts
Strongly Typed
IDE Autocompletion
Better know language (for Scala Dev)
Single Language Codebase

64. Weaknes
Big Result Files
Harder Debugging
Don't part of JS Ecosystem
Lack of Support to many libraries (fe. Akka and Guice)
Performance payoffs and don't able to perfomance by hand

65. Opportunities
Our Holy Grail :)
More Scalable Codebase
Chances to more library support in future
Creators promise better performance

66. Treats /
Concerns
Project will loose interests and support
Every Abstraction Leaks :(

67. Links
Activator: play-scalajs-showcase
http://lihaoyi.github.io/hands-on-scala-js/
http://www.scala-js-fiddle.com/
http://ochrons.github.io/scalajs-spa-tutorial/

68. Thank You