Language.Javascript.JSaddle

This package provides an EDSL for calling JavaScript that can be used both from GHCJS and GHC. When using GHC the application is run using Warp and WebSockets to drive a small JavaScipt helper.

JSaddle EDSL

The JSM monad gives us the context for evaluation. In keeping with JavaScript the EDSL has

• Weakish typing - type classes are used to convert to JSValueRef and Object types
• Strict evaluation - function in the JSM monad can be passed in place of a value and will evaluated and converted to JSValueRef or Object and then passed on to JavaScript

JSaddle should be used to write wrappers for JavaScript libraries that provide more type safety.

Code Examples

The code examples in this documentation are executed with a runjs function that executes the example code in the JSM monad and converts the result to Text with valToText. It also catches unhandled exceptions with catch. The source code can be found in tests/TestJSaddle.hs

Where it makes sense code examples are given in two forms. One that uses eval to run a purely JavaScript version and one that uses more of the JSaddle EDSL feature being demonstated.

Calling Haskell from JavaScript

You can call back into haskell from JavaScript using fun to convert a Haskell function in the JSM monad into a javascript value.

GHCJS Support

When built with ghcjs the code works using JavaScript FFI by default.

GHC Support

When built with ghc the code runs a small Warp server that provides index.html and jsaddle.js files. When a browser is connected the code in jsaddle.js will open a WebSockets connection to the server and the server will run the Haskell code. The JSaddle parts will be executed by sending commands back to the browser.

Modules