JavaScript on Scala -Nashorn-

Introduction of Nashorn.
JavaScript runtime on JVM, also on Scala.

Transcript

1. JavaScript on Scala
   AdTech ✕ Scala MeetUp
   Fringe81 Co., Ltd.
   @petitviolet
   

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2. Nashorn
   

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3. Nashorn 㱺
   +7.
   

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4. What is Nashorn?
   • JavaScript runtime on JVM
   㱺 JavaScript on Scala!!!
   • Project Nashorn
   • http://openjdk.java.net/projects/nashorn/
   

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5. 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")

   }
   

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6. 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
   

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7. 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
   

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8. 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
   

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9. Procedure
   • Preparation
   • create ScriptEngine
   • Compilation
   • compile String as a JavaScript function
   • Execution
   • feed AnyRef arguments to ScriptEngine
   

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10. ↑↑↑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, …
    

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11. ↓↓↓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!!!
    

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12. 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
    

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13. Happy Hacking!
    We’re hiring!
    

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