Simple ScalaJS "Speed Reader" example

SpeedReader.scala

//https://scalafiddle.io/sf/55sE0OL/10

import scalatags.JsDom.all._
import org.scalajs.dom
import fiddle.Fiddle.panel

val wpm = 300d

val group = 1

val interval = 60 / wpm * group * 1000

val message = """Speed reading is any of several techniques used to improve one's ability to read quickly. 
Speed reading methods include chunking and minimizing subvocalization. 
The many available speed reading training programs include books, videos, software, and seminars."""

val tokens = message.split("\\s+").grouped(group).map(_.mkString(" ")).toList ++ List("")

def start(again: Boolean = false): Unit = println(button((if (again) "Restart" else "Start"), onclick := { () =>

  var i = 0

  var intervalHandle = 0

  intervalHandle = dom.window.setInterval(() => {
    while (panel.childElementCount > 0)
      panel.removeChild(panel.firstChild)
    if (i < tokens.size) {
      panel.appendChild(
        div(
          padding := "10px",
          id := "page",
          h1(
            margin := "auto",
            textAlign := "center",
            tokens(i))).render)
      i = i + 1
    } else {
      dom.window.clearInterval(intervalHandle)
      start(again = true)
    }
  }, interval)
}))


start()

updated to current scalafiddle.io