Refined Types

demo.ts

interface UserInput {
  age: Number
}

var input = JSON.parse("{\"age\": \"hello\"}") as UserInput

console.log(typeof(input.age))

refined.scala

import eu.timepit.refined.api.{Refined}
import eu.timepit.refined.boolean._
import eu.timepit.refined.string._

object Types {
  type userEmail = String Refined MatchesRegex[".*@gmail.com"]
  type ipAddress = String Refined IPv4 Or IPv6
}