Using Parcel JS with Tailwind CSS, Elm Lang and Elm Spa

 - Vincent Jousse

As I have been struggling to make Parcel JS, Tailwind CSS, PostCSS, whatever-the-hell-you-call-it-CSS, Elm Lang and Elm SPA work together I thought that sharing my journey could help some of you. Here it is!

TL;DR

The final boilerplate source code is available on Github.

The bonus version with elm-spa is also available on Github in the elm-spa branch.

Why?

My initial need was: using Taiwind CSS with Elm Lang and Elm Spa. It quickly turned into a journey through the classical Javascript fatigue tools and my new need was: find something that just get the job done. Spoiler: it’s the case with Parcel JS.

Parcel JS

This bundler just works. We will be using the v2 here (as I had a lot of problems to make the v1 work) so be sure to check the v2 documentation: https://v2.parceljs.org/ (note the v2 in the URL).

Parcel is a compiler for all your code, regardless of the language or toolchain.

Parcel takes all of your files and dependencies, transforms them, and merges them together into a smaller set of output files that can be used to run your code.

package.json

{
  "name": "my-program",
  "version": "1.0.0",
  "devDependencies": {
    "parcel": "latest"
  }
}

Then just npm install.

Then let’s create directories for every type of file we’re going to have (src/ will contain the elm files):

.
├── css
├── src
├── html
└── js

Put an example index.html file in your html folder:

<!doctype html>
<html lang="en">
  <head>
    <meta charset="utf-8"/>
    <title>My First Parcel App</title>
    <link rel="stylesheet" href="../css/styles.css" />
    <script type="module" src="../js/app.js"></script>
  </head>
  <body>
    <h1>Hello, World!</h1>
  </body>
</html>

Then a styles.css file in your css folder:

h1 {
  color: hotpink;
  font-family: cursive;
}

And an app.js file in your js folder:

console.log('Hello world!');

Then modify your package.json to include some parcel scripts:

{
  "name": "my-program",
  "version": "1.0.0",
  "scripts": {
    "start": "parcel html/index.html",
    "build": "parcel build html/index.html"
  },
  "devDependencies": {
    "parcel": "latest"
  }
}

Run npm start and visit http://localhost:1234 in your browser, you should get something like that:

Parcel Hello World

Let’s add Tailwind CSS

Tailwind CSS

Install Tailwind CSS and its dependencies:

npm install -D tailwindcss@latest postcss@latest autoprefixer@latest

Add tailwindcss and autoprefixer as plugins in a .postcssrc.json file that you should create.

.postcssrc.json

{
  "plugins": {
    "tailwindcss": {},
    "autoprefixer": {}
  }
}

Then, the next step is to create the configuration file for Tailwind with the following command:

npx tailwindcss init

This should create a tailwind.config.js file with the following content:

module.exports = {
  purge: [],
  darkMode: false, // or 'media' or 'class'
  theme: {
    extend: {},
  },
  variants: {
    extend: {},
  },
  plugins: [],
}

Finally, incude Tailwind in your styles.css file:

@tailwind base;
@tailwind components;
@tailwind utilities;

h1 {
  color: hotpink;
  font-family: cursive;
}

Now you can modify your index.html page by adding some Tailwind CSS classes in it.

<!doctype html>
<html lang="en">
  <head>
    <meta charset="utf-8"/>
    <title>My First Parcel App</title>
    <link rel="stylesheet" href="../css/styles.css" />
    <script type="module" src="../js/app.js"></script>
  </head>
  <body class="bg-gray-200">
    <h1 class="text-4xl">Hello, World!</h1>
    <p class="text-green-500">Testing Tailwind</p>
  </body>
</html>

This should display something like that:

Parcel Hello World Tailwind

Ok now, let’s add some Elm!

Elm

First, install the latest Elm version with npm:

npm install -D elm@latest-0.19.1

Then create an elm.json file yourself or let the init script do it for you using npx elm init. Here is my elm.json file:

{
    "type": "application",
    "source-directories": [
        "src"
    ],
    "elm-version": "0.19.1",
    "dependencies": {
        "direct": {
            "elm/browser": "1.0.2",
            "elm/core": "1.0.5",
            "elm/html": "1.0.0"
        },
        "indirect": {
            "elm/json": "1.1.3",
            "elm/time": "1.0.0",
            "elm/url": "1.0.0",
            "elm/virtual-dom": "1.0.2"
        }
    },
    "test-dependencies": {
        "direct": {},
        "indirect": {}
    }
}

Then create a Main.elm file in your src directory with the following content:

module Main exposing (..)

import Browser
import Html exposing (Html, button, div, text)
import Html.Attributes exposing (class)
import Html.Events exposing (onClick)


main =
    Browser.sandbox { init = init, update = update, view = view }


type alias Model =
    Int


init : Model
init =
    0


type Msg
    = Increment
    | Decrement


update : Msg -> Model -> Model
update msg model =
    case msg of
        Increment ->
            model + 1

        Decrement ->
            model - 1


view : Model -> Html Msg
view model =
    div [ class "m-10 text-4xl" ]
        [ button [ onClick Decrement ] [ text "-" ]
        , div [ class "text-green-400" ] [ text (String.fromInt model) ]
        , button [ onClick Increment ] [ text "+" ]
        ]

Modify your index.html:

html/index.html

<!doctype html>
<html lang="en">
  <head>
    <meta charset="utf-8"/>
    <title>My First Parcel App</title>
    <link rel="stylesheet" href="../css/styles.css" />
    <script type="module" src="../js/app.js"></script>
  </head>
  <body>
    <div id="myapp"></div>
  </body>
</html>

And include your Elm program inside your javascript.

js/app.js

import { Elm } from '../src/Main.elm';

Elm.Main.init({ node: document.getElementById('myapp') });

Run npm start and go to http://localhost:1234/ you should see the Elm counter demo with some Tailwind styles:

Parcel Hello World Tailwind Elm

Purging CSS classes

To avoid to include all the unused Tailwind CSS classes in the outputed CSS, configure your tailwind.config.js file by adding some directory to the purge entry:

module.exports = {
  purge: [
    './src/**/*.elm',
    './js/app.js',
    './html/index.html',
    './css/styles.css',
  ],
  darkMode: false, // or 'media' or 'class'
  theme: {
    extend: {},
  },
  variants: {
    extend: {},
  },
  plugins: [],
};

You can now build your code and you should find everything you need in the dist/ folder.

npm run build

The output should be something like that:

> my-program@1.0.0 build
> parcel build html/index.html

✨ Built in 178ms

dist/index.html               250 B    646ms
dist/index.96cb94bc.css     3.67 KB    243ms
dist/index.e73152c4.js     15.89 KB    598ms

Adding elm-spa

As a little bonus, we will see how to add elm-spa to our project.

First install the needed dependencies:

npm install -D chokidar-cli elm-spa elm-test npm-run-all

And change the package.json to add the scripts below:

"scripts": {
  "start": "npm install && npm run build:dev && npm run dev",
  "test": "elm-test",
  "test:watch": "elm-test --watch",
  "build": "run-s build:elm-spa build:elm",
  "build:dev": "run-s build:elm-spa build:dev:elm",
  "dev": "run-p dev:elm-spa dev:elm",
  "build:elm": "parcel build html/index.html",
  "build:dev:elm": "elm make src/Main.elm --debug --output=public/dist/elm.compiled.js || true",
  "build:elm-spa": "elm-spa build .",
  "dev:elm": "parcel html/index.html",
  "dev:elm-spa": "chokidar elm/ -c \"npm run build:elm-spa\""
},

This will give you a lot of new commands to play with like npm run dev, npm run build, and so on.

Delete our example file in elm/Main.elm and init elm-spa in the current directory using:

npx elm-spa init

Answer yes to init the project. Remove the public/index.html that has been created and use the default Main.elm from elm-spa.

mv .elm-spa/defaults/Main.elm src

It should have changed part of your elm.json with some new dependencies and new source code directories.

And now, if everything goes well, npm run build should work as expected!

The full code is available on Github.