Copy\Duplicate a file with AppleScript (javascript)

Hello,

I am trying to copy files using AppleScript(javascript) and for the life of me cannot figure out the correct syntax. I have tried all the possible variations i can think of the following but nothing seems to work. Any suggestions would be greatly appreciated!.

var app = Application.currentApplication()
app.includeStandardAdditions = true

// Tried this
app.duplicate("/tmp/file1.txt"), {
  to: "/tmp/file2.txt"
})
// And all sorts of variations such as
app.duplicate(Path("/tmp/file1.txt"), {
  to: Path("/tmp/file2.txt")
})
// And not including file names
app.duplicate("/tmp/file1.txt"), {
  to: "/tmp/"
})