Scala.js: How do I read the value using of an input element using Scala.js? - scala.js

Question

I am trying to do something like this:
<input id="test">Hello!</input>
import io.udash.wrappers.jquery.jQ
// Read from Scala
val x = jQ("#test").value().asIntanceOf[String]
But, I get a ClassCastException saying String | Int | Double | js.Array[Any] cannot be cast to a String

Answer 1

I came up with a typeclass approach (which hides the ugly asInstanceOf):
import scala.scalajs.js.|
import scala.util.Try
trait JsRead[A] { self =>
import JsRead.Or
def apply(value: Or): Option[A]
def map[B](f: A => Option[B]): JsRead[B] = new JsRead[B] {
override def apply(value: Or) = self.apply(value).flatMap(f)
}
}
object JsRead {
type Or = _ | _
def apply[A](f: Or => Option[A]): JsRead[A] = new JsRead[A] {
override def apply(value: Or) = f(value)
}
implicit class Dsl(value: Or) {
def as[A](implicit reader: JsRead[A]): Option[A] =
reader(value)
}
implicit val string: JsRead[String] = JsRead(x => Try(x.asInstanceOf[String]).toOption)
implicit val int: JsRead[Int] = string.map(_.toIntOption)
implicit val double: JsRead[Double] = string.map(_.toDoubleOption)
}
Now I can use it as:
import io.udash.wrappers.jquery.{jQ => $}
for {
deposit <- $("#deposit").value().as[Int]
monthlyWithdrawal <- $("#monthlyWithdrawal").value().as[Int]
irr <- $("#irr").value().as[Double]
inflation <- $("#inflation").value().as[Double]
year <- $("#year").value().as[Int]
} {
// do something
}