# CoreUI & Webpack

> The official guide for how to include and bundle CoreUI's CSS and JavaScript in your project using Webpack.

## What is Webpack?

[Webpack](https://webpack.js.org/) is a JavaScript module bundler that processes modules and their dependencies to generate static assets. It simplifies managing complex web applications with multiple files and dependencies.

## Setup

We're building a Webpack project with CoreUI from scratch, so there are some prerequisites and upfront steps before we can really get started. This guide requires you to have Node.js installed and some familiarity with the terminal.

1. **Create a project folder and set up npm.** We'll create the `my-project` folder and initialize npm with the `-y` argument to avoid it asking us all the interactive questions.

   ```sh
   mkdir my-project && cd my-project
   npm init -y
   ```

   Current npm versions write `"type": "commonjs"` into that fresh `package.json`. Delete that line. Our `src/js/main.js` is written with `import`, and under `"type": "commonjs"` Webpack refuses to parse it (*'import' and 'export' may appear only with 'sourceType: module'*). With no `type` field, Webpack detects the module system per file, so the ESM source and the CommonJS `webpack.config.js` below both work.

2. **Install Webpack.** Next we need to install our Webpack development dependencies: `webpack` for the core of Webpack, `webpack-cli` so we can run Webpack commands from the terminal, and `webpack-dev-server` so we can run a local development server. We use `--save-dev` to signal that these dependencies are only for development use and not for production.

   ```sh
   npm i --save-dev webpack webpack-cli webpack-dev-server
   ```

3. **Install CoreUI.** Now we can install CoreUI. We'll also install Floating UI since our dropdowns, popovers, and tooltips depend on it for their positioning. If you don't plan on using those components, you can omit Floating UI here.

   ```sh
   npm i --save @coreui/coreui @floating-ui/dom
   ```

   **For PRO users**

   ```sh
   npm i --save @coreui/coreui-pro @floating-ui/dom
   ```

4. **Install additional dependencies.** In addition to Webpack and CoreUI, we need a few more dependencies to properly import and bundle CoreUI's CSS and JS with Webpack. These include Sass, some loaders, and Autoprefixer.

   ```sh
   npm i --save-dev autoprefixer css-loader postcss-loader sass sass-loader style-loader
   ```

Now that we have all the necessary dependencies installed, we can get to work creating the project files and importing CoreUI.

## Project structure

We've already created the `my-project` folder and initialized npm. Now we'll also create our `src` and `dist` folders to round out the project structure. Run the following from `my-project`, or manually create the folder and file structure shown below.

```sh
mkdir {dist,src,src/js,src/scss}
touch dist/index.html src/js/main.js src/scss/styles.scss webpack.config.js
```

When you're done, your complete project should look like this:

```text
my-project/
├── dist/
│   └── index.html
├── src/
│   ├── js/
│   │   └── main.js
│   └── scss/
│       └── styles.scss
├── package-lock.json
├── package.json
└── webpack.config.js
```

At this point, everything is in the right place, but Webpack won't work because we haven't filled in our `webpack.config.js` yet.

## Configure Webpack

With dependencies installed and our project folder ready for us to start coding, we can now configure Webpack and run our project locally.

1. **Open `webpack.config.js` in your editor.** Since it's blank, we'll need to add some boilerplate config to it so we can start our server. This part of the config tells Webpack where to look for our project's JavaScript, where to output the compiled code to (`dist`), and how the development server should behave (pulling from the `dist` folder with hot reload).

   ```js
   const path = require('path')

   module.exports = {
     entry: './src/js/main.js',
     output: {
       filename: 'main.js',
       path: path.resolve(__dirname, 'dist')
     },
     devServer: {
       static: path.resolve(__dirname, 'dist'),
       port: 8080,
       hot: true
     }
   }
   ```

2. **Next we fill in our `dist/index.html`.** This is the HTML page Webpack will load in the browser to utilize the bundled CSS and JS we'll add to it in later steps. Before we can do that, we have to give it something to render and include the `output` JS from the previous step.

   ```html
   <!doctype html>
   <html lang="en">
     <head>
       <meta charset="utf-8">
       <meta name="viewport" content="width=device-width, initial-scale=1">
       <title>CoreUI w/ Webpack</title>
     </head>
     <body>
       <div class="container py-5 px-4 mx-auto">
         <h1>Hello, CoreUI and Webpack!</h1>
         <button class="btn-solid theme-primary">Primary button</button>
       </div>
       
     </body>
   </html>
   ```

   We're including a little bit of CoreUI styling here with the `div class="container"` and `<button>` so that we see when CoreUI's CSS is loaded by Webpack.

3. **Now we need an npm script to run Webpack.** Open `package.json` and add the `start` script shown below (you should already have the test script). We'll use this script to start our local Webpack dev server.

   ```json
   {
     // ...
     "scripts": {
       "start": "webpack serve --mode development",
       "test": "echo \"Error: no test specified\" && exit 1"
     },
     // ...
   }
   ```

4. **And finally, we can start Webpack.** From the `my-project` folder in your terminal, run that newly added npm script:

   ```sh
   npm start
   ```

In the next and final section to this guide, we'll set up the Webpack loaders and import all of CoreUI's CSS and JavaScript.

## Import CoreUI

Importing CoreUI into Webpack requires the loaders we installed in the first section. We've installed them with npm, but now Webpack needs to be configured to use them.

1. **Set up the loaders in `webpack.config.js`.** Your configuration file is now complete and should match the snippet below. The only new part here is the `module` section.

   ```js
   const path = require('path')

   module.exports = {
     entry: './src/js/main.js',
     output: {
       filename: 'main.js',
       path: path.resolve(__dirname, 'dist')
     },
     devServer: {
       static: path.resolve(__dirname, 'dist'),
       port: 8080,
       hot: true
     },
     module: {
       rules: [
         {
           test: /\.(scss)$/,
           use: [
             {
               loader: 'style-loader'
             },
             {
               loader: 'css-loader'
             },
             {
               loader: 'postcss-loader',
               options: {
                 postcssOptions: {
                   plugins: [
                     require('autoprefixer')
                   ]
                 }
               }
             },
             {
               loader: 'sass-loader'
             }
           ]
         }
       ]
     }
   }
   ```

   Here's a recap of why we need all these loaders. `style-loader` injects the CSS into a `<style>` element in the `<head>` of the HTML page, `css-loader` helps with using `@import` and `url()`, `postcss-loader` is required for Autoprefixer, and `sass-loader` allows us to use Sass.

2. **Now, let's import CoreUI's CSS.** Add the following to `src/scss/styles.scss` to import all of CoreUI's source Sass. `sass-loader` resolves the package name through `node_modules`, so the path needs no `~` prefix and no alias.

   ```scss
   // Use all of CoreUI's CSS
   @use "@coreui/coreui/scss/coreui";
   ```

   PRO users import the PRO package instead. Import **one** of the two — importing both emits the whole stylesheet twice.

   ```scss
   @use "@coreui/coreui-pro/scss/coreui";
   ```

   *You can also import our stylesheets individually if you want. [Read our Sass import docs](https://coreui.io/bootstrap/docs/customize/sass/#importing) for details.*

3. **Next we load the CSS and import CoreUI's JavaScript.** Add the following to `src/js/main.js` to load the CSS and import all of CoreUI's JS. Floating UI will be imported automatically through CoreUI.

   ```js
   // Import our custom CSS
   import '../scss/styles.scss'

   // Import all of CoreUI's JS
   import * as coreui from '@coreui/coreui'
   ```

   PRO users import the PRO package instead. Again, pick one — two `import * as coreui` statements in the same file bind the same name twice and the file will not parse.

   ```js
   import * as coreui from '@coreui/coreui-pro'
   ```

   You can also import JavaScript plugins individually as needed to keep bundle sizes down:

   ```js
   import Alert from '@coreui/coreui/js/dist/alert'

   // or, specify which plugins you need:
   import { Tooltip, Toast, Popover } from '@coreui/coreui'
   ```

   *[Read our JavaScript docs](https://coreui.io/bootstrap/docs/getting-started/javascript/) for more information on how to use CoreUI's plugins.*

4. **And you're done! 🎉** With CoreUI's source Sass and JS fully loaded and running at `http://localhost:8080`, you can start adding any CoreUI components you want to use.

## Production optimizations

Depending on your setup, you may want to implement some additional security and speed optimizations useful for running the project in production.

### Extracting CSS

The `style-loader` we configured above conveniently emits CSS into the bundle so that manually loading a CSS file in `dist/index.html` isn't necessary. This approach may not work with a strict Content Security Policy, however, and it may become a bottleneck in your application due to the large bundle size.

To separate the CSS so that we can load it directly from `dist/index.html`, use the `mini-css-extract-loader` Webpack plugin.

First, install the plugin:

```sh
npm install --save-dev mini-css-extract-plugin
```

Then instantiate and use the plugin in the Webpack configuration:

```diff
--- a/webpack/webpack.config.js
+++ b/webpack/webpack.config.js
@@ -1,8 +1,10 @@
+const miniCssExtractPlugin = require('mini-css-extract-plugin')
 const path = require('path')

 module.exports = {
   mode: 'development',
   entry: './src/js/main.js',
+  plugins: [new miniCssExtractPlugin()],
   output: {
     filename: "main.js",
     path: path.resolve(__dirname, "dist"),
@@ -18,8 +20,8 @@ module.exports = {
         test: /\.(scss)$/,
         use: [
           {
-            // Adds CSS to the DOM by injecting a `<style>` tag
-            loader: 'style-loader'
+            // Extracts CSS for each JS file that includes CSS
+            loader: miniCssExtractPlugin.loader
           },
           {
```

After running `npm run build` again, there will be a new file `dist/main.css`, which will contain all of the CSS imported by `src/js/main.js`. If you view `dist/index.html` in your browser now, the style will be missing, as it is now in `dist/main.css`. You can include the generated CSS in `dist/index.html` like this:

```diff
--- a/webpack/dist/index.html
+++ b/webpack/dist/index.html
@@ -3,6 +3,7 @@
   <head>
     <meta charset="utf-8">
     <meta name="viewport" content="width=device-width, initial-scale=1">
+    <link rel="stylesheet" href="./main.css">
     <title>CoreUI w/ Webpack</title>
   </head>
   <body>
```

### Extracting SVG files

CoreUI's CSS includes multiple references to SVG files via inline `data:` URIs. If you define a Content Security Policy for your project that blocks `data:` URIs for images, then these SVG files will not load. You can get around this problem by extracting the inline SVG files using Webpack's asset modules feature.

Configure Webpack to extract inline SVG files like this:

```diff
--- a/webpack/webpack.config.js
+++ b/webpack/webpack.config.js
@@ -16,6 +16,14 @@ module.exports = {
   },
   module: {
     rules: [
+      {
+        mimetype: 'image/svg+xml',
+        scheme: 'data',
+        type: 'asset/resource',
+        generator: {
+          filename: 'icons/[hash].svg'
+        }
+      },
       {
         test: /\.(scss)$/,
         use: [
```

After running `npm run build` again, you'll find the SVG files extracted into `dist/icons` and properly referenced from CSS.