I love Swift and work on the web, so I would love to see a serious Swift to JS compiler. Unfortunately, this isn't it.

One major part of Swift is its value types; many core types, including arrays, are passed by value, like a C struct. So

  var a = [1, 2]
  var b = a
  b.append(3)

should make `a` equal to [1, 2] and `b` equal to [1, 2, 3]. ShiftJS eschews these semantics and instead passes arrays (and other value types) by reference, which makes it basically impossible to share code between real Swift and ShiftJS.

Also, the demo compiles

  let a = 3 4

to

  var a = '3 4';

which doesn't instill confidence.