Interactive development tool that makes it easy to develop and debug Elm programs. Key features include:
- Automatically compile any Elm program
- Hot-swapping
- Time travel debugging
- Compatible with any editor
This means you can get a great development experience whether you are using Sublime Text, emacs, vim, or whatever else to edit Elm code.
Install Elm Platform. This will install Elm Reactor and everything else it needs.
Navigate to the Elm project you want to work on. A great project to get started with is elm-examples which contains a simple Mario game and todo list app, both setup to be fun to debug.
In the root of your Elm project start the reactor with:
elm-reactor
Now open http://localhost:8000 in your browser. You should see a navigation page for your project.
Click on any file to see what it looks like. For example, you can navigate to an Elm file and try it out. If you modify the file, you can just refresh that page and see the new version!
To use the debugger, click the small wrench next to every Elm file. This will start your Elm program with a control panel that lets you:
-
Pause, rewind, and continue from any point.
-
Add watches and traces to track and visualize values over time.
-
Hot-swap in new code at any time, maintaining all recorded events.
To use the debugger with more complex HTML or CSS, you may want to start the debugger from within an HTML file.
In your custom HTML file load the /debugger.js
script right after you load
elm-runtime:
<script type="text/javascript" src="/elm-runtime.js"></script>
<script type="text/javascript" src="/debugger.js"></script>
That creates the Elm.debugFullscreen
function so you can initiate your Elm
program with the debugger:
var runningElmModule = Elm.debugFullscreen(Elm.Todo, "todo.elm");
The argument "todo.elm"
is the file path to the root module of your project,
the one with a main
value. This file path makes it possible to hot-swap when
you change any relevant code.