Install Elm

The previous page described how to install a code editor for Elm, so the next step is to obtain an executable file named elm. Here are the install links:

Mac - installer
Linux - instructions
Windows - installer

After installation is complete, open up the terminal on your computer. It may be called cmd.exe or Command Prompt on Windows.

Start by navigating to your desktop in the terminal:

# Mac and Linux
cd ~/Desktop

# Windows (but with <username> filled in with your user name)
cd C:\Users\<username>\Desktop

The next step is to get familiar with elm command. I personally had a really hard time learning terminal commands, so I worked hard to make the elm command nice to use. Let's go through a couple common scenarios.

elm init

You can start an Elm project by running:

elm init

Try running this command to create an elm.json file and a src/ directory:

elm.json describes your project.
src/ holds all of your Elm files.

Now try creating a file called src/Main.elm in your editor, and copying in the code from the buttons example.

elm reactor

elm reactor helps you build Elm projects without messing with the terminal too much. You just run it at the root of your project, like this:

elm reactor

This starts a server at http://localhost:8000. You can navigate to any Elm file and see what it looks like. Run elm reactor, follow the localhost link, and try to check out your src/Main.elm file!

elm make

You can compile Elm code to HTML or JavaScript with commands like this:

# Create an index.html file that you can open in your browser.
elm make src/Main.elm

# Create an optimized JS file to embed in a custom HTML document.
elm make src/Main.elm --optimize --output=elm.js

Try running these commands on your src/Main.elm file.

This is the most general way to compile Elm code. It is extremely useful once your project becomes too advanced for elm reactor.

This command produces the same messages you have been seeing in the online editor and with elm reactor. Years of work has gone into them so far, but please report any unhelpful messages here. I am sure there are ways to improve!

elm install

Elm packages all live at package.elm-lang.org.

Say you look around and decide you need elm/http and elm/json to make some HTTP requests. You can get them set up in your project with the following commands:

elm install elm/http
elm install elm/json

This adds these dependencies into your elm.json file, making these packages available in your project. That will let you say import Http and use functions like Http.get in your programs.

Tips and Tricks

First, do not worry about remembering all this stuff!

You can always run elm --help to get a full outline of what elm is capable of.

You can also run commands like elm make --help and elm repl --help to get hints about a specific command. This is great if you want to check which flags are available and what they do.

Second, do not worry if it takes some time to get comfortable with the terminal in general.

I have been using it for over a decade now, and I still cannot remember how to compress files, find all Elm files in a directory, etc. I still look a lot of things up!

Now that we have our editor set up and elm available in the terminal, let's get back to learning Elm!

Elm