We are very excited about the upcoming Yesod 1.2 release, but we should mention other improvements in the Yesod ecosystem. There are some greate updates to shakespeare-js are available today.
- Dramatically faster template reloads
- Support for TypeScript on unix
- Roy integration supports variable interpolation
Faster template reloads
In production code, shakespeare compiles everything once to static strings awaiting some variable insertions. In developement mode, it is preferred to use the shakespeare functions that automatically reload their file contents such as coffeeFileReload. This means that on every web request the file will be re-parsed in case it changed. This works great, but when using an external service such as coffee-script, there is a noticeable lag to shell out to the compiler. So the reload functions now cache the file contents in memory and only reload them when the modification time of the file changes.
TypeScript support on unix
TypeScript is now supported on unix in the same way that CoffeeScript has been. We should be able to make it work on Windows if there is interest.
The biggest problem with TypeScript is the lack of type inference and presence of null. Coming from Haskell you might expect the type to be inferred when it is obvious to you that it could be, but it will often end up just being a dynamic type unless you write down a type annotation for every function. However, you still may be able to achieve some strong typing with less effort if you are leveraging existing type declaration files for the frameworks you are using, like these: https://github.com/borisyankov/DefinitelyTyped
Knowledge of TypeScript, like CoffeeScript, is a skill that is portable outside of the Haskell community.
Roy variable interpretation
Roy templates now support variable interpolation.
Of course you can use whatever you want on the client side. Those mentioned here have existing packages for easy integration with Yesod. ghcjs is continually being improved and is another option for compiling Haskell (and the only option for Haskell using more than the Fay subset), and there are examples available for usage with Yesod.