Scala.js allows code written in the Scala programming language to be compiled to JavaScript. It is an alternative JavaScript (AltJS) that allows Scala code to create JavaScript. Some key features of Scala.js include: - Compiling Scala code to JavaScript that can run in web browsers or with Node.js - Using familiar Scala concepts like classes, collections, and functions when writing code - Statically typed for catching errors early and better integration with IDEs

1. What is Scala.js?
Nov. 16, 2019
Kazuhisa Kawashima

2. Who am I
● Name : Kazuhisa Kawashima
● Home : Shizuoka shi, aoi ku
● Company : YUMEMI inc.
● Job : Computer Engineer
● Favorite computer language : Scala, TypeScript

3. What is Yumemi?
Company Features
● We are a software engineering company.
● We value the growth of everyone.
● All employees are CEOs.
● The salary is decided by yourself.
● We decide all things by the proposal request.
Reference : https://note.mu/raykataoka/n/n50c282bcb305

4. What is Scala.js?

5. Scala.js is ...
● One of the AltJS
● Create JavaScript from code written in Scala
Scala JavaScript
AltJS
Scala.js
TypeScript
Kotlin.js
CoffeeScript
translate

6. Example code

7. Classes
class Person {
constructor(public firstName: string, public lastName: string) {
}
fullName() {
return `${this.firstName} ${this.lastName}`;
}
}
class Person(val firstName: String, val lastName: String) {
def fullName(): String = s”${firstName} ${lastName}”
}
Scala.js
TypeScript

8. Collections
const personMap = new Map<number, Person>([
[10, new Person(“Roger”, ”Moore”)],
[20, new Person(“James”, “Bond”)]
]);
const names = new Array<string>();
for (const [key, person] of personMap) {
if (key > 15) {
names.push(`${key} = ${person.firstName}`);
}
}
val personMap = Map(
10 -> Person(“Roger”, ”Moore”),
20 -> Person(“James”, “Bond”)
)
val names = for {
(key, person) <- personMap if key > 15
} yield s”$key = ${person.firstName}”
Scala.jsTypeScript

9. What can you do with Scala.js

10. On the node.js
AWS Cloud
Node.js
npm
module
Scala.js
AWS SDK
for JavaScript

11. On the web browser
Web browser
Scala.js
Storage Rest Client
Framework(for instance, Vue.js)
JavaScript / TypeScript
View

12. What is Scala？

13. Scala is
● Fusion of OOP and FP
● Statically typed
● Interaction with Java language
● It takes longer to learn than other languages

14. Fusion of OOP and FP
Object oriented
language
Procedures
Data
Functional
language
Side
effects
exclude
fusion
Stateexclude

15. Statically typed
If you use Scala ...
● The compiler check simple mistake before running.
○ Missing a type
○ Typo
○ Missing number of arguments
● You’ll be able to use the IDE effectivery
○ Autocomplete
○ Refactoring

16. ● When you compile Scala code, it becomes a class file.
● Scala PG run on the Java VM.
Interaction with Java language
Java VM
Class file
(Scala)
Class file
(Java)
call
Scala Class file
compile

17. It takes time to learn longer...
MonadComplex
language
specification
Type class
Implicit Functional
It’s too
difficult!

18. Don’t worry about it!

19. You can start to use Scala from better Java!
val list = List(1, 2, 3, 4, 5, 6, 7, 8, 9)
var sum = 0
list foreach(i => sum = sum + i)
val list = List(1, 2, 3, 4, 5, 6, 7, 8, 9)
val sum = list.foldLeft(0) {(s, i) => s + i}
You can also use var! Let’s start to change var to val!

20. Scalapedia
https://scalapedia.com/
プログラミング言語Scalaは、金融機関、クラウド事業者、広告配
信、モバイル・Webアプリケーションなどの業界で広く使われてい
ます。 処理が高速で、かつ堅牢で安全なプログラムを構築できま
す。 そのうえ、豊かな表現力によりコンパクトで保守性の高いプ
ログラムを実現できるのが特徴です。
I’m writing an
article in
Scalapedia!

21. Scala Next

22. Loadmap
● Now : version 2.13.1
● Scala 3 (Dotty)
To be released in the fall of 2020
● Next : version 2.14
For easy migration to Scala 3

23. Finally
We are hiring!
Yumemi Recruit Information
Welcome who want to work in Shizuoka with me!
● Twitter : @cupperservice
● E-mail : k_kawashima@yumemi.co.jp

24. Thank you for listening!