The Foreign Function Interface (FFI) for interacting with JavaScript

To define a foreign module, make a new module and add use ElixirScript.FFI. to it To define external functions, use the defexternal macro.

Here is an example of a foreign module for a JSON module

defmodule MyApp.JSON do
  use ElixirScript.FFI

  defexternal stringify(map)
  defexternal parse(string)
end

Foreign modules map to JavaScript files that export functions defined with the defexternal macro. ElixirScript expects JavaScript modules to be in the priv/elixir_script directory. These modules are copied to the output directory upon compilation.

For our example, a JavaScript file must be placed in the priv/elixir_script folder. In our example, it could either be priv/elixir_script/my_app/json.js or priv/elixir_script/my_app.json.js. ElixirScript will look for either path

It looks like this

export default {
  stringify: JSON.stringify,
  parse: JSON.parse
}

ElixirScript.FFI takes the following options

• global: If the module is defined in the global state or not. If this is set to true, nothing is imported and instead ElixirScript will use the name of the module to call a module and function in the global scope.
• name: Only applicable with global is set to true. This will use the name defined here instead of the module name for calling modules and functions in the global scope

An example using the global option to reference the JSON module in browsers

defmodule JSON do
  use ElixirScript.FFI, global: true

  defexternal stringify(map)
  defexternal parse(string)
end

The calls above are translated to calls to the JSON module in the global scope

An example using global and name options

defmodule Console do
  use ElixirScript.FFI, global: true, name: :console

  defexternal log(term)
end

With the above, calls in ElixirScript to Console.log will translate to console.log in JavaScript