d3 key function demo

key_function_demo.log

iteration 1
key( 11,12,13 | 11 | 0) was 'this' an array? true
key( 11,12,13 | 12 | 1) was 'this' an array? true
key( 11,12,13 | 13 | 2) was 'this' an array? true
iteration 2
key( [object HTMLDivElement] | 11 | 0) was 'this' an array? false
key( [object HTMLDivElement] | 12 | 1) was 'this' an array? false
key( [object HTMLDivElement] | 13 | 2) was 'this' an array? false
key( 11,12,13 | 11 | 0) was 'this' an array? true
key( 11,12,13 | 12 | 1) was 'this' an array? true
key( 11,12,13 | 13 | 2) was 'this' an array? true
iteration 3
key( [object HTMLDivElement] | 11 | 0) was 'this' an array? false
key( [object HTMLDivElement] | 12 | 1) was 'this' an array? false
key( [object HTMLDivElement] | 13 | 2) was 'this' an array? false
key( 11,12,13 | 11 | 0) was 'this' an array? true
key( 11,12,13 | 12 | 1) was 'this' an array? true
key( 11,12,13 | 13 | 2) was 'this' an array? true

KeyFunctionDemo.scala

package test

import scala.scalajs.js
import org.singlespaced.d3js.d3
import org.singlespaced.d3js.selection.Update

object KeyFunctionDemo extends js.JSApp {

  def main() = {
    for(i <- 1 to 3) {
      println(s"iteration $i")
      exercise
    }
  }

  def exercise = {
    val s: Update[Int] = d3.select("body").selectAll("div").data(numbers, key_func)
    s.enter.append("div")
    s.text((d: Int, i: Int, j: js.UndefOr[Int]) => d.toString)
  }

  def key_func: js.ThisFunction2[Any, js.UndefOr[Int], Int, String] = {
    (t: Any, d: js.UndefOr[Int], i: Int) =>
      println(s"key( $t | $d | $i) was 'this' an array? ${js.Array.isArray(t.asInstanceOf[js.Any])}")
      i.toString
  }

  def numbers = js.Array(11, 12, 13)
}