JavaScript Interoperability

Data Type Conversions

ElixirScript translates Elixir primitive types to the following:

Elixir	JavaScript
Integer	Number
Float	Number
Binary	String
Atom	Symbol
List	Array
Map	Map
Tuple	ErlangTypes.Tuple
Bitstring	ErlangTypes.Bitstring
PID	ErlangTypes.PID
Reference	ErlangTypes.Reference

The ErlangTypes library can be found here

ElixirScript Calling JavaScript

ElixirScript.JS module

The ElixirScript.JS module has functions and macros that help with interacting with JavaScript. Most of them correspond to JavaScript keywords that may be useful.

# Calling the JavaScript Debugger
ElixirScript.JS.debugger()

# Getting the type of a value
ElixirScript.JS.typeof(my_value)

Foreign Function Interface

ElixirScript calls JavaScript modules through a Foreign Function Interface (FFI). A foreign module is defined by creating a new Elixir module and adding use ElixirScript.FFI to it.

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 at priv/elixir_script/my_app/json.js.

It looks like this

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

For more information and options. Check the documentation for ElixirScript.FFI

JavaScript Calling ElixirScript

In order to start an ElixirScript application, you must first import it using whichever JavaScript module system you are using and then call Elixir.start

  # Our ElixirScript module

  defmodule Main do
    def start(:normal, args) do
      args
    end
  end

  import Main from './Elixir.Main.js'
  Main.start(Symbol.for('normal'), [1, 2, 3])

In the above example, we have an ElixirScript module, Main with a start/2 function.

If you want to use an ElixirScript module inside of your JavaScript code, you can do so like below.

  # Our ElixirScript module

  defmodule MyModule do
    def hi() do
      "hello"
    end
  end

  import MyModule from './Elixir.MyModule.js'
  MyModule.hi()