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https://github.com/cultureamp/elm-css-modules-loader

Reference CSS modules in Elm source files with Webpack
https://github.com/cultureamp/elm-css-modules-loader

css css-modules elm elm-lang webpack webpack-loader

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Reference CSS modules in Elm source files with Webpack

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README 

        
# CSS Modules for Elm



A [Webpack][webpack] loader that enables you to reference CSS modules in Elm

source files.



Hat tip to NoRedInk and its [elm-assets-loader][elm-assets-loader], which

formed the technical basis for this package.



## Overview



Start with a CSS file that can be imported by Webpack using

[css-loader][css-loader]:



```css

.something {

  ⋮

}



.anotherThing {

  ⋮

}

```



In any Elm module, reference this stylesheet and the classes you want to use in

it:



```elm

module Main exposing (..)



import CssModules exposing (css)



styles =

    css "./stylesheet.css" -- relative to main Elm source directory

        { something = "something" -- string value should match CSS class name 

        , anotherThing = "anotherThing"

        }

```



Then use the returned functions to use the class names in your view:



```elm

view : Html Msg

view =

    div

        [ styles.class .something ]

        [ text "this is a div"]

```



**Note:** the `.something` syntax may be confusing at first. This is just standard Elm syntax for a function that reaches into a record and returns the value of the `something` key. Because the Elm compiler will only let you reference class names that exist in your CSS Module declaration, you get a bit of type safety to guard against typing mistakes.



## Why does this exist?



We wanted to use the same style sheets for the standard components in our

application (buttons, form fields, etc.) across two different implementations

of these components ([React][react] and [Elm][elm]). We love the namespacing and

composition features of [CSS Modules][css-modules]; this project seeks to make

them usable within Elm views.



**Note:** [elm-css][elm-css] is the de facto standard for writing styles for

HTML interfaces written in Elm. If you are working on an all-Elm application,

you should probably use that.



## How to use



To get this working, you need to set up a combination of a Webpack loader and

and Elm package.



### Webpack Loader



Add the `elm-css-modules-loader` NPM package to your project, then configure

Webpack to chain it with [elm-webpack-loader][elm-webpack-loader]:



#### Webpack 2+



```javascript

module.exports = {

  ⋮

  module: {

    rules: [

      {

        test: /\.elm$/,

        use: [

          {

            loader: 'elm-css-modules-loader',

          },

          {

            loader: 'elm-webpack',

          }

        ],

      },

      ⋮

    ],

  },

};

```



#### Webpack 1.x



```javascript

module.exports = {

  ⋮

  module: {

    loaders: [

      {

        test: /\.elm$/,

        loaders: [

          'elm-css-modules-loader',

          'elm-webpack',

        ],

      },

      ⋮

    ],

  },

};

```



Note the following configuration options are available for the loader. If you’re

using the original version of this package, the defaults should work fine.



`package` – (default: `cultureamp/elm-css-modules-loader`) The Elm package in

which the `CssModule` type is defined. If you forked the Elm package for your

own development, you’ll need to specify the full package name that you have

released it under with this option.



`module` – (default: `CssModules`) The name of the Elm module in which the

`tagger` function is defined.



`tagger` – (default: `css`) The name of the Elm factory function that is used

to declare CssModules in your code.



**Note:** Don't set `noParse` on .elm files. Otherwise, the JavaScript `require`s that this loader adds to your compiled Elm modules won't be processed by Webpack.



### Elm Package



Install the `cultureamp/elm-css-modules-loader` package in your Elm project,

then use the `CssModule` constructor for referencing CSS modules.



## Under the hood



Let’s walk through what happens when this Elm code is processed by Webpack:



```elm

styles =

    css "./stylesheet.css"

        { something = "something"

        , anotherThing = "anotherThing"

        }

```



This will be compiled to JavaScript by elm-webpack-loader:



```js

var user$project$Styles$styles = A2(

  cultureamp$elm_css_modules_loader$CssModules$css,

  './stylesheet.css',

  {

    aC: 'something',

    aD: 'anotherThing'

  }

);

```



elm-css-modules-loader replaces the hard-coded JSON object with a `require` of your stylesheet:



```js

var user$project$Styles$styles = A2(

  cultureamp$elm_css_modules_loader$CssModules$css,

  './stylesheet.css',

  {

    aC: require('./stylesheet.css')["something"],

    aD: require('./stylesheet.css')["anotherThing"]

  }

);

```



webpack parses this `require` call, processes the stylesheet with css-loader, and replaces the `require` with a reference to the CSS module:



```js

var user$project$Styles$styles = A2(

  cultureamp$elm_css_modules_loader$CssModules$css,

  './stylesheet.css',

  {

    aC: __webpack_require__(42)["something"],

    aD: __webpack_require__(42)["anotherThing"]

  }

);

```



The CSS module loaded by `__webpack_require__(42)` contains the actual class names that your Elm app will now consume:



```js

42:

function(module, exports) {

  module.exports = {

    something: 'something-abc123',

    anotherThing: 'anotherThing-abc123'

  };

}

```



[css-loader]: https://www.npmjs.com/package/css-loader

[css-modules]: https://github.com/css-modules/css-modules

[elm]: http://elm-lang.org

[elm-assets-loader]: https://github.com/NoRedInk/elm-assets-loader

[elm-css]: https://github.com/rtfeldman/elm-css

[elm-webpack-loader]: https://www.npmjs.com/package/elm-webpack-loader

[react]: https://facebook.github.io/react/

[webpack]: https://webpack.js.org



## Changelog



Our release history is tracked on the [Github Releases page](https://github.com/cultureamp/elm-css-modules-loader/releases).



Note that the NPM package and the Elm package will have different version numbers, as changes to the Elm API may happen indepently of changes to the NPM API, and Elm does not allow you to bump the version number without changes to the Elm API. When viewing the releases page, NPM releases are tagged with a "v" - `v2.1.0`. While Elm releases are tagged with no leading "v" - `2.0.3`.



For release history prior to 2.0.2, you can view our [old CHANGELOG](https://github.com/cultureamp/elm-css-modules-loader/blob/6afcae3f61439f9a0f05cb84bb6a1aea2f1acd81/CHANGELOG.md)

.



---



Elm CSS Modules Loader is maintained by the Front End Capability Team at Culture Amp.