Slide 1
Slide 1 text
JavaScript on Scala
AdTech ✕ Scala MeetUp
Fringe81 Co., Ltd.
@petitviolet
Slide 2
Slide 2 text
Nashorn
Slide 3
Slide 3 text
Nashorn 㱺
+7.
Slide 4
Slide 4 text
What is Nashorn?
• JavaScript runtime on JVM
㱺 JavaScript on Scala!!!
• Project Nashorn
• http://openjdk.java.net/projects/nashorn/
Slide 5
Slide 5 text
Example
https://goo.gl/1KrXoo
object NashornExample extends App {
val ENGINE_NAME = "nashorn"
val engine = new ScriptEngineManager()
.getEngineByName(ENGINE_NAME)
.asInstanceOf[ScriptEngine with Invocable]
val fName = "func"
val f = s"function $fName(a, b) { return a + b; };"
engine.asInstanceOf[Compilable].compile(f).eval()
val argments = Seq(1, 2) map { _.asInstanceOf[AnyRef] }
val result = engine.invokeFunction(fName, argments:_*)
println(s"result => $result")
}
Slide 6
Slide 6 text
object NashornExample extends App {
val ENGINE_NAME = "nashorn"
val engine = new ScriptEngineManager()
.getEngineByName(ENGINE_NAME)
.asInstanceOf[ScriptEngine with Invocable]
val fName = "func"
val f = s"function $fName(a, b) { return a + b; };"
engine.asInstanceOf[Compilable].compile(f).eval()
val argments = Seq(1, 2) map { _.asInstanceOf[AnyRef] }
val result = engine.invokeFunction(fName, argments:_*)
println(s"result => $result")
}
Preparation
Example
https://goo.gl/1KrXoo
Slide 7
Slide 7 text
object NashornExample extends App {
val ENGINE_NAME = "nashorn"
val engine = new ScriptEngineManager()
.getEngineByName(ENGINE_NAME)
.asInstanceOf[ScriptEngine with Invocable]
val fName = "func"
val f = s"function $fName(a, b) { return a + b; };"
engine.asInstanceOf[Compilable].compile(f).eval()
val argments = Seq(1, 2) map { _.asInstanceOf[AnyRef] }
val result = engine.invokeFunction(fName, argments:_*)
println(s"result => $result")
}
Compilation
Example
https://goo.gl/1KrXoo
Slide 8
Slide 8 text
object NashornExample extends App {
val ENGINE_NAME = "nashorn"
val engine = new ScriptEngineManager()
.getEngineByName(ENGINE_NAME)
.asInstanceOf[ScriptEngine with Invocable]
val fName = "func"
val f = s"function $fName(a, b) { return a + b; };"
engine.asInstanceOf[Compilable].compile(f).eval()
val argments = Seq(1, 2) map { _.asInstanceOf[AnyRef] }
val result = engine.invokeFunction(fName, argments:_*)
println(s"result => $result")
}
Execution
Example
https://goo.gl/1KrXoo
Slide 9
Slide 9 text
Procedure
• Preparation
• create ScriptEngine
• Compilation
• compile String as a JavaScript function
• Execution
• feed AnyRef arguments to ScriptEngine
Slide 10
Slide 10 text
↑↑↑ʘ(^o^)ʗ↑↑↑
• Store JavaScript functions in DB as Strings
• Use stored functions as Scala function!
• Enable replacing algorithms dynamically
• e.g. Scoring, Sorting, Selection, …
Slide 11
Slide 11 text
↓↓↓ʗ(^o^)ʘ↓↓↓
• Static typing(Scala) <=> Dynamic typing(JS)
• lose type information
• Unexpected input causes unexpected output
• e.g. null, NaN, Infinity, ReferenceError, …
• Cannot avoid such results with compilation
• Runtime!!!
Slide 12
Slide 12 text
Lose type information?
• No
• Can use Java types in JavaScript
• Java.Type(“”)
• https://docs.oracle.com/javase/jp/8/docs/technotes/guides/scripting/nashorn/api.html
• Enable casting a result of execution
• asInstanceOf[T]
• https://gist.github.com/petitviolet/4c446066da25c150a0eb50b39b4522d3
Slide 13
Slide 13 text
Happy Hacking!
We’re hiring!