martinmullins/compiler

Compiler for Elm, a functional language for reliable webapps.

The Elm Compiler + JS Modules

• This feature branch reintroduces JS modules for any elm application or package

Install

• I pulled the npm package and binaries because I jumped the gun on the actual 0.19.1 elm release
• To build manually install stack: https://docs.haskellstack.org/en/stable/README/#how-to-install then:

git clone ..
stack build

# The binary is then in:
echo $(stack path --local-install-root)/bin/elm[.exe]

Example

• elm init
• Create a Javascript module, src/Elm/Kernel/JS.js
• Important notes:
  • Javascript modules must be in a Elm/Kernel/ folder

// Nothing crazy here, the JS.log function logs the string and returns it
function _JS_log(s) {
    console.log(s);
    return s;
}

• Create an Elm module to call our javascript, src/Main.elm

module Main exposing(..)

import Html exposing (..)
import Elm.Kernel.JS

log : String -> String
log = Elm.Kernel.JS.log

main = text <| log <| "HelloWorld"

• Compile elm make src/Main.elm
• Open index.html
  • "HelloWorld" should be printed to the console and on the page
• More js module examples are here elm/core library.