html-loader/README.md

Html loader module for webpack

<div align="center">
  <img width="200" height="200" src="https://worldvectorlogo.com/logos/html5.svg" alt="html-loader">
  <a href="https://github.com/webpack/webpack">
    <img width="200" height="200" vspace="" hspace="25" src="https://webpack.js.org/assets/icon-square-big.svg" alt="webpack">
  </a>
</div>

[![npm][npm]][npm-url]
[![node][node]][node-url]
[![deps][deps]][deps-url]
[![tests][tests]][tests-url]
[![coverage][cover]][cover-url]
[![chat][chat]][chat-url]
[![size][size]][size-url]

# html-loader

Exports HTML as string. HTML is minimized when the compiler demands.

## Getting Started

To begin, you'll need to install `html-loader`:

```console
npm install --save-dev html-loader
```

Then add the plugin to your `webpack` config. For example:

**file.js**

```js
import html from './file.html';
```

**webpack.config.js**

```js
module.exports = {
  module: {
    rules: [
      {
        test: /\.html$/i,
        loader: 'html-loader',
      },
    ],
  },
};
```

## Options

|                Name                 |        Type         |                   Default                    | Description                                      |
| :---------------------------------: | :-----------------: | :------------------------------------------: | :----------------------------------------------- |
|      **[`sources`](#sources)**      | `{Boolean\|Object}` |                    `true`                    | Enables/Disables sources handling                |
| **[`preprocessor`](#preprocessor)** |    `{Function}`     |                 `undefined`                  | Allows pre-processing of content before handling |
|     **[`minimize`](#minimize)**     | `{Boolean\|Object}` | `true` in production mode, otherwise `false` | Tell `html-loader` to minimize HTML              |
|     **[`esModule`](#esmodule)**     |     `{Boolean}`     |                    `true`                    | Enable/disable ES modules syntax                 |

### `sources`

Type: `Boolean|Object`
Default: `true`

By default every loadable attributes (for example - `<img src="image.png">`) is imported (`const img = require('./image.png')` or `import img from "./image.png""`).
You may need to specify loaders for images in your configuration (recommended [`asset modules`](https://webpack.js.org/guides/asset-modules/)).

Supported tags and attributes:

- the `src` attribute of the `audio` tag
- the `src` attribute of the `embed` tag
- the `src` attribute of the `img` tag
- the `srcset` attribute of the `img` tag
- the `src` attribute of the `input` tag
- the `data` attribute of the `object` tag
- the `src` attribute of the `script` tag
- the `href` attribute of the `script` tag
- the `xlink:href` attribute of the `script` tag
- the `src` attribute of the `source` tag
- the `srcset` attribute of the `source` tag
- the `src` attribute of the `track` tag
- the `poster` attribute of the `video` tag
- the `src` attribute of the `video` tag
- the `xlink:href` attribute of the `image` tag
- the `href` attribute of the `image` tag
- the `xlink:href` attribute of the `use` tag
- the `href` attribute of the `use` tag
- the `href` attribute of the `link` tag when the `rel` attribute contains `stylesheet`, `icon`, `shortcut icon`, `mask-icon`, `apple-touch-icon`, `apple-touch-icon-precomposed`, `apple-touch-startup-image`, `manifest`, `prefetch`, `preload` or when the `itemprop` attribute is `image`, `logo`, `screenshot`, `thumbnailurl`, `contenturl`, `downloadurl`, `duringmedia`, `embedurl`, `installurl`, `layoutimage`
- the `imagesrcset` attribute of the `link` tag when the `rel` attribute contains `stylesheet`, `icon`, `shortcut icon`, `mask-icon`, `apple-touch-icon`, `apple-touch-icon-precomposed`, `apple-touch-startup-image`, `manifest`, `prefetch`, `preload`
- the `content` attribute of the `meta` tag when the `name` attribute is `msapplication-tileimage`, `msapplication-square70x70logo`, `msapplication-square150x150logo`, `msapplication-wide310x150logo`, `msapplication-square310x310logo`, `msapplication-config`, `twitter:image` or when the `property` attribute is `og:image`, `og:image:url`, `og:image:secure_url`, `og:audio`, `og:audio:secure_url`, `og:video`, `og:video:secure_url`, `vk:image` or when the `itemprop` attribute is `image`, `logo`, `screenshot`, `thumbnailurl`, `contenturl`, `downloadurl`, `duringmedia`, `embedurl`, `installurl`, `layoutimage`
- the `icon-uri` value component in `content` attribute of the `meta` tag when the `name` attribute is `msapplication-task`

#### `Boolean`

The `true` value enables processing of all default elements and attributes, the `false` disable processing of all attributes.

**webpack.config.js**

```js
module.exports = {
  module: {
    rules: [
      {
        test: /\.html$/i,
        loader: 'html-loader',
        options: {
          // Disables attributes processing
          sources: false,
        },
      },
    ],
  },
};
```

#### `Object`

Allows you to specify which tags and attributes to process, filter them, filter urls and process sources starts with `/`.

For example:

**webpack.config.js**

```js
module.exports = {
  module: {
    rules: [
      {
        test: /\.html$/i,
        loader: 'html-loader',
        options: {
          sources: {
            list: [
              // All default supported tags and attributes
              '...',
              {
                tag: 'img',
                attribute: 'data-src',
                type: 'src',
              },
              {
                tag: 'img',
                attribute: 'data-srcset',
                type: 'srcset',
              },
            ],
            urlFilter: (attribute, value, resourcePath) => {
              // The `attribute` argument contains a name of the HTML attribute.
              // The `value` argument contains a value of the HTML attribute.
              // The `resourcePath` argument contains a path to the loaded HTML file.

              if (/example\.pdf$/.test(value)) {
                return false;
              }

              return true;
            },
          },
        },
      },
    ],
  },
};
```

#### `list`

Type: `Array`
Default: [supported tags and attributes](#sources).

Allows to setup which tags and attributes to process and how, and the ability to filter some of them.

Using `...` syntax allows you to extend [default supported tags and attributes](#sources).

For example:

**webpack.config.js**

```js
module.exports = {
  module: {
    rules: [
      {
        test: /\.html$/i,
        loader: 'html-loader',
        options: {
          sources: {
            list: [
              // All default supported tags and attributes
              '...',
              {
                tag: 'img',
                attribute: 'data-src',
                type: 'src',
              },
              {
                tag: 'img',
                attribute: 'data-srcset',
                type: 'srcset',
              },
              {
                // Tag name
                tag: 'link',
                // Attribute name
                attribute: 'href',
                // Type of processing, can be `src` or `scrset`
                type: 'src',
                // Allow to filter some attributes
                filter: (tag, attribute, attributes, resourcePath) => {
                  // The `tag` argument contains a name of the HTML tag.
                  // The `attribute` argument contains a name of the HTML attribute.
                  // The `attributes` argument contains all attributes of the tag.
                  // The `resourcePath` argument contains a path to the loaded HTML file.

                  if (/my-html\.html$/.test(resourcePath)) {
                    return false;
                  }

                  if (!/stylesheet/i.test(attributes.rel)) {
                    return false;
                  }

                  if (
                    attributes.type &&
                    attributes.type.trim().toLowerCase() !== 'text/css'
                  ) {
                    return false;
                  }

                  return true;
                },
              },
            ],
          },
        },
      },
    ],
  },
};
```

If the tag name is not specified it will process all the tags.

> You can use your custom filter to specify html elements to be processed.

For example:

**webpack.config.js**

```js
module.exports = {
  module: {
    rules: [
      {
        test: /\.html$/i,
        loader: 'html-loader',
        options: {
          sources: {
            list: [
              {
                // Attribute name
                attribute: 'src',
                // Type of processing, can be `src` or `scrset`
                type: 'src',
                // Allow to filter some attributes (optional)
                filter: (tag, attribute, attributes, resourcePath) => {
                  // The `tag` argument contains a name of the HTML tag.
                  // The `attribute` argument contains a name of the HTML attribute.
                  // The `attributes` argument contains all attributes of the tag.
                  // The `resourcePath` argument contains a path to the loaded HTML file.

                  // choose all HTML tags except img tag
                  return tag.toLowerCase() !== 'img';
                },
              },
            ],
          },
        },
      },
    ],
  },
};
```

Filter can also be used to extend the supported elements and attributes. For example, filter can help process meta tags that reference assets:

```js
module.exports = {
  module: {
    rules: [
      {
        test: /\.html$/i,
        loader: 'html-loader',
        options: {
          sources: {
            list: [
              {
                tag: 'meta',
                attribute: 'content',
                type: 'src',
                filter: (tag, attribute, attributes, resourcePath) => {
                  if (
                    attributes.value === 'og:image' ||
                    attributes.name === 'twitter:image'
                  ) {
                    return true;
                  }
                  return false;
                },
              },
            ],
          },
        },
      },
    ],
  },
};
```

#### `urlFilter`

Type: `Function`
Default: `undefined`

Allow to filter urls. All filtered urls will not be resolved (left in the code as they were written).
All non requestable sources (for example `<img src="javascript:void(0)">`) do not handle by default.

```js
module.exports = {
  module: {
    rules: [
      {
        test: /\.html$/i,
        loader: 'html-loader',
        options: {
          sources: {
            urlFilter: (attribute, value, resourcePath) => {
              // The `attribute` argument contains a name of the HTML attribute.
              // The `value` argument contains a value of the HTML attribute.
              // The `resourcePath` argument contains a path to the loaded HTML file.

              if (/example\.pdf$/.test(value)) {
                return false;
              }

              return true;
            },
          },
        },
      },
    ],
  },
};
```

### `preprocessor`

Type: `Function`
Default: `undefined`

Allows pre-processing of content before handling.

> ⚠ You should always return valid HTML

**file.hbs**

```hbs
<div>
  <p>{{firstname}} {{lastname}}</p>
  <img src="image.png" alt="alt" />
<div>
```

#### `Function`

You can set the `preprocessor` option as a `Function` instance.

**webpack.config.js**

```js
const Handlebars = require('handlebars');

module.exports = {
  module: {
    rules: [
      {
        test: /\.hbs$/i,
        loader: 'html-loader',
        options: {
          preprocessor: (content, loaderContext) => {
            let result;

            try {
              result = Handlebars.compile(content)({
                firstname: 'Value',
                lastname: 'OtherValue',
              });
            } catch (error) {
              loaderContext.emitError(error);

              return content;
            }

            return result;
          },
        },
      },
    ],
  },
};
```

You can also set the `preprocessor` option as an asynchronous function instance.

For example:

**webpack.config.js**

```js
const Handlebars = require('handlebars');

module.exports = {
  module: {
    rules: [
      {
        test: /\.hbs$/i,
        loader: 'html-loader',
        options: {
          preprocessor: async (content, loaderContext) => {
            let result;

            try {
              result = await Handlebars.compile(content)({
                firstname: 'Value',
                lastname: 'OtherValue',
              });
            } catch (error) {
              await loaderContext.emitError(error);

              return content;
            }

            return result;
          },
        },
      },
    ],
  },
};
```

### `minimize`

Type: `Boolean|Object`
Default: `true` in production mode, otherwise `false`

Tell `html-loader` to minimize HTML.

#### `Boolean`

The enabled rules for minimizing by default are the following ones:

```js
({
  caseSensitive: true,
  collapseWhitespace: true,
  conservativeCollapse: true,
  keepClosingSlash: true,
  minifyCSS: true,
  minifyJS: true,
  removeComments: true,
  removeRedundantAttributes: true,
  removeScriptTypeAttributes: true,
  removeStyleLinkTypeAttributes: true,
});
```

**webpack.config.js**

```js
module.exports = {
  module: {
    rules: [
      {
        test: /\.html$/i,
        loader: 'html-loader',
        options: {
          minimize: true,
        },
      },
    ],
  },
};
```

#### `Object`

**webpack.config.js**

See [html-minifier-terser](https://github.com/DanielRuf/html-minifier-terser)'s documentation for more information on the available options.

The rules can be disabled using the following options in your `webpack.conf.js`

**webpack.config.js**

```js
module.exports = {
  module: {
    rules: [
      {
        test: /\.html$/i,
        loader: 'html-loader',
        options: {
          minimize: {
            removeComments: false,
            collapseWhitespace: false,
          },
        },
      },
    ],
  },
};
```

### `esModule`

Type: `Boolean`
Default: `true`

By default, `html-loader` generates JS modules that use the ES modules syntax.
There are some cases in which using ES modules is beneficial, like in the case of [module concatenation](https://webpack.js.org/plugins/module-concatenation-plugin/) and [tree shaking](https://webpack.js.org/guides/tree-shaking/).

You can enable a CommonJS modules syntax using:

**webpack.config.js**

```js
module.exports = {
  module: {
    rules: [
      {
        test: /\.html$/i,
        loader: 'html-loader',
        options: {
          esModule: false,
        },
      },
    ],
  },
};
```

## Examples

### roots

With [`resolve.roots`](https://webpack.js.org/configuration/resolve/#resolveroots) can specify a list of directories where requests of server-relative URLs (starting with '/') are resolved.

**webpack.config.js**

```js
module.exports = {
  context: __dirname,
  module: {
    rules: [
      {
        test: /\.html$/i,
        loader: 'html-loader',
        options: {},
      },
      {
        test: /\.jpg$/,
        type: 'asset/resource',
      },
    ],
  },
  resolve: {
    roots: [path.resolve(__dirname, 'fixtures')],
  },
};
```

**file.html**

```html
<img src="/image.jpg" />
```

```js
// => image.jpg in __dirname/fixtures will be resolved
```

### CDN

**webpack.config.js**

```js
module.exports = {
  module: {
    rules: [
      {
        test: /\.jpg$/,
        type: 'asset/resource',
      },
      {
        test: /\.png$/,
        type: 'asset/inline',
      },
    ],
  },
  output: {
    publicPath: 'http://cdn.example.com/[hash]/',
  },
};
```

**file.html**

```html
<img src="image.jpg" data-src="image2x.png" />
```

**index.js**

```js
require('html-loader!./file.html');

// => '<img src="http://cdn.example.com/49eba9f/a992ca.jpg" data-src="image2x.png">'
```

```js
require('html-loader?{"sources":{"list":[{"tag":"img","attribute":"data-src","type":"src"}]}}!./file.html');

// => '<img src="image.jpg" data-src="data:image/png;base64,..." >'
```

```js
require('html-loader?{"sources":{"list":[{"tag":"img","attribute":"src","type":"src"},{"tag":"img","attribute":"data-src","type":"src"}]}}!./file.html');

// => '<img src="http://cdn.example.com/49eba9f/a992ca.jpg" data-src="data:image/png;base64,..." >'
```

```js
require('html-loader?-sources!./file.html');

// => '<img src="image.jpg"  data-src="image2x.png" >'
```

> :warning: `-sources` sets `sources: false`.

### Process `script` and `link` tags

**script.file.js**

```js
console.log(document);
```

**style.file.css**

```css
a {
  color: red;
}
```

**file.html**

```html
<!DOCTYPE html>
<html>
  <head>
    <meta charset="UTF-8" />
    <title>Title of the document</title>
    <link rel="stylesheet" type="text/css" href="./style.file.css" />
  </head>
  <body>
    Content of the document......
    <script src="./script.file.js"></script>
  </body>
</html>
```

**webpack.config.js**

```js
module.exports = {
  module: {
    rules: [
      {
        test: /\.html$/,
        type: 'asset/resource',
        generator: {
          filename: '[name][ext]',
        },
      },
      {
        test: /\.html$/i,
        use: ['extract-loader', 'html-loader'],
      },
      {
        test: /\.js$/i,
        exclude: /\.file.js$/i,
        loader: 'babel-loader',
      },
      {
        test: /\.file.js$/i,
        type: 'asset/resource',
      },
      {
        test: /\.css$/i,
        exclude: /\.file.css$/i,
        loader: 'css-loader',
      },
      {
        test: /\.file.css$/i,
        type: 'asset/resource',
      },
    ],
  },
};
```

### Templating

You can use any template system. Below is an example for [handlebars](https://handlebarsjs.com/).

**file.hbs**

```hbs
<div>
  <p>{{firstname}} {{lastname}}</p>
  <img src="image.png" alt="alt" />
<div>
```

**webpack.config.js**

```js
const Handlebars = require('handlebars');

module.exports = {
  module: {
    rules: [
      {
        test: /\.hbs$/i,
        loader: 'html-loader',
        options: {
          preprocessor: (content, loaderContext) => {
            let result;

            try {
              result = Handlebars.compile(content)({
                firstname: 'Value',
                lastname: 'OtherValue',
              });
            } catch (error) {
              loaderContext.emitError(error);

              return content;
            }

            return result;
          },
        },
      },
    ],
  },
};
```

### PostHTML

You can use [PostHTML](https://github.com/posthtml/posthtml) without any additional loaders.

**file.html**

```html
<img src="image.jpg" />
```

**webpack.config.js**

```js
const posthtml = require('posthtml');
const posthtmlWebp = require('posthtml-webp');

module.exports = {
  module: {
    rules: [
      {
        test: /\.hbs$/i,
        loader: 'html-loader',
        options: {
          preprocessor: (content, loaderContext) => {
            let result;

            try {
              result = posthtml().use(plugin).process(content, { sync: true });
            } catch (error) {
              loaderContext.emitError(error);

              return content;
            }

            return result.html;
          },
        },
      },
    ],
  },
};
```

### Export into HTML files

A very common scenario is exporting the HTML into their own _.html_ file, to
serve them directly instead of injecting with javascript. This can be achieved
with a combination of 2 loaders:

- [extract-loader](https://github.com/peerigon/extract-loader)
- html-loader

and [`asset modules`](https://webpack.js.org/guides/asset-modules/)

The html-loader will parse the URLs, require the images and everything you
expect. The extract loader will parse the javascript back into a proper html
file, ensuring images are required and point to proper path, and the [`asset modules`](https://webpack.js.org/guides/asset-modules/)
will write the _.html_ file for you. Example:

**webpack.config.js**

```js
module.exports = {
  output: {
    assetModuleFilename: '[name][ext]',
  },
  module: {
    rules: [
      {
        test: /\.html$/,
        type: 'asset/resource',
        generator: {
          filename: '[name][ext]',
        },
      },
      {
        test: /\.html$/i,
        use: ['extract-loader', 'html-loader'],
      },
    ],
  },
};
```

## Contributing

Please take a moment to read our contributing guidelines if you haven't yet done so.

[CONTRIBUTING](./.github/CONTRIBUTING.md)

## License

[MIT](./LICENSE)

[npm]: https://img.shields.io/npm/v/html-loader.svg
[npm-url]: https://npmjs.com/package/html-loader
[node]: https://img.shields.io/node/v/html-loader.svg
[node-url]: https://nodejs.org
[deps]: https://david-dm.org/webpack-contrib/html-loader.svg
[deps-url]: https://david-dm.org/webpack-contrib/html-loader
[tests]: https://github.com/webpack-contrib/html-loader/workflows/html-loader/badge.svg
[tests-url]: https://github.com/webpack-contrib/html-loader/actions
[cover]: https://codecov.io/gh/webpack-contrib/html-loader/branch/master/graph/badge.svg
[cover-url]: https://codecov.io/gh/webpack-contrib/html-loader
[chat]: https://img.shields.io/badge/gitter-webpack%2Fwebpack-brightgreen.svg
[chat-url]: https://gitter.im/webpack/webpack
[size]: https://packagephobia.now.sh/badge?p=html-loader
[size-url]: https://packagephobia.now.sh/result?p=html-loader