PureScript may soon be a serious contender in the HKT language category. It is more or less a strict Haskell for JavaScript runtimes with some new type system features like row types and more fine-grained control over I/O (see http://www.purescript.org/learn/eff/ and https://github.com/purescript/purescript/wiki/Differences-fr...). It has an experimental native (via C++11) backend.