If it's a small part of your system take that one that integrates best: JS => Purescript, JVM => Scala, .NET => F# etc. I wouldn't call Scala3 quite "start-a-p

If it's a small part of your system take that one that integrates best: JS => Purescript, JVM => Scala, .NET => F# etc. I wouldn't call Scala3 quite "start-a-project-with-it" ready because the ecosystem will need a couple of months at least to update, but Scala 2.13 should suit your needs more than fine.