HTML Loader srcset

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

Variant of the html-loader module for Webpack with a patch to load srcset attribute(s) and actually produces valid tags

Install

npm i --save-dev html-loader-srcset

Usage

By default every local <img src="image.png"> is required (require('./image.png')). You may need to specify loaders for images in your configuration (recommended file-loader or url-loader).

Also every <img srcset="..."> is converted to require statements. For example

<img src="image.jpg" srcset="image.jpg 1x, [e-mail] 2x">

is converted to

"<img src=\"" + require("./image.jpg") + "\" srcset=\"" + require("./image.jpg") + " 1x, " + require("./[e-mail]") + " 2x \">"

You can specify which tag-attribute combination should be processed by this loader via the query parameter attrs. Pass an array or a space-separated list of <tag>:<attribute> combinations. (Default: attrs=[img:src, img:srcset]). The srcset-specific qualifiers such as 100w or 3x are supported in any processed attribute.

If you use <custom-elements>, and lots of them make use of a custom-src attribute, you don't have to specify each combination <tag>:<attribute>: just specify an empty tag like attrs=:custom-src and it will match every element.

{
  test: /\.(html)$/,
  use: {
    loader: 'html-loader-srcset',
    options: {
      attrs: [':data-src']
    }
  }
}

To completely disable tag-attribute processing (for instance, if you're handling image loading on the client side) you can pass in attrs=false.

Examples

With this configuration:

{
  module: {
    rules: [
      { test: /\.jpg$/, use: [ "file-loader" ] },
      { test: /\.png$/, use: [ "url-loader?mimetype=image/png" ] }
    ]
  },
  output: {
    publicPath: "http://cdn.example.com/[hash]/"
  }
}

<!-- file.html -->
<img src="image.png" data-src="image2x.png" >

require("html-loader-srcset!./file.html");
 
// => '<img src="http://cdn.example.com/49eba9f/a992ca.png"
//         data-src="image2x.png">'

require("html-loader-srcset?attrs=img:data-src!./file.html");
 
// => '<img src="image.png" data-src="data:image/png;base64,..." >'

require("html-loader-srcset?attrs=img:src img:data-src!./file.html");
require("html-loader-srcset?attrs[]=img:src&attrs[]=img:data-src!./file.html");
 
// => '<img  src="http://cdn.example.com/49eba9f/a992ca.png"        
//           data-src="data:image/png;base64,..." >'

require("html-loader-srcset?-attrs!./file.html");
 
// => '<img  src="image.jpg"  data-src="image2x.png" >'

minimized by running webpack --optimize-minimize

'<img src=http://cdn.example.com/49eba9f/a9f92ca.jpg
      data-src=data:image/png;base64,...>'

or specify the minimize property in the rule's options in your webpack.conf.js

module: {
  rules: [{
    test: /\.html$/,
    use: [ {
      loader: 'html-loader-srcset',
      options: {
        minimize: true
      }
    }],
  }]
}

See html-minifier's documentation for more information on the available options.

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

• removeComments
• removeCommentsFromCDATA
• removeCDATASectionsFromCDATA
• collapseWhitespace
• conservativeCollapse
• removeAttributeQuotes
• useShortDoctype
• keepClosingSlash
• minifyJS
• minifyCSS
• removeScriptTypeAttributes
• removeStyleTypeAttributes

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

module: {
  rules: [{
    test: /\.html$/,
    use: [ {
      loader: 'html-loader-srcset',
      options: {
        minimize: true,
        removeComments: false,
        collapseWhitespace: false
      }
    }],
  }]
}

'Root-relative' URLs

For urls that start with a /, the default behavior is to not translate them. If a root query parameter is set, however, it will be prepended to the url and then translated.

With the same configuration as above:

<!-- file.html -->
<img src="/image.jpg">

require("html-loader-srcset!./file.html");
 
// => '<img  src="/image.jpg">'

require("html-loader-srcset?root=.!./file.html");
 
// => '<img  src="http://cdn.example.com/49eba9f/a992ca.jpg">'

Interpolation

You can use interpolate flag to enable interpolation syntax for ES6 template strings, like so:

require("html-loader-srcset?interpolate!./file.html");

<img src="${require(`./images/gallery.png`)}">
 
<div>${require('./components/gallery.html')}</div>

And if you only want to use require in template and any other ${} are not to be translated, you can set interpolate flag to require, like so:

require("html-loader-srcset?interpolate=require!./file.ftl");

 
<#list list as list>
  <a href="${list.href!}" />${list.name}</a>
</#list>
 
<img src="${require(`./images/gallery.png`)}">
 
<div>${require('./components/gallery.html')}</div>

Export formats

There are different export formats available:

• module.exports (default, cjs format). "Hello world" becomes module.exports = "Hello world";
• exports.default (when exportAsDefault param is set, es6to5 format). "Hello world" becomes exports.default = "Hello world";
• export default (when exportAsEs6Default param is set, es6 format). "Hello world" becomes export default "Hello world";

Advanced options

If you need to pass more advanced options, especially those which cannot be stringified, you can also define an htmlLoader-property on your webpack.config.js:

var path = require('path')
 
module.exports = {
  ...
  module: {
    rules: [
      {
        test: /\.html$/,
        use: [ "html-loader-srcset" ]
      }
    ]
  },
  htmlLoader: {
    ignoreCustomFragments: [/\{\{.*?}}/],
    root: path.resolve(__dirname, 'assets'),
    attrs: ['img:src', 'link:href']
  }
};

If you need to define two different loader configs, you can also change the config's property name via html-loader-srcset?config=otherHtmlLoaderConfig:

module.exports = {
  ...
  module: {
    rules: [
      {
        test: /\.html$/,
        use: [ "html-loader-srcset?config=otherHtmlLoaderConfig" ]
      }
    ]
  },
  otherHtmlLoaderConfig: {
    ...
  }
};

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 3 loaders:

• file-loader
• extract-loader
• html-loader-srcset

The html-loader-srcset 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 file loader will write the .html file for you. Example:

{
  test: /\.html$/,
  use: ['file-loader?name=[name].[ext]', 'extract-loader', 'html-loader-srcset'],
}

Maintainers

Hemanth	Joshua Wiens	Michael Ciniawsky	Imvetri
Andrei Crnković	Yuta Hiroto	Vesselin Petrunov	Gajus Kuizinas