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    @vtex/style-loader

    0.21.1 • Public • Published

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    Style Loader

    Adds CSS to the DOM by injecting a <style> tag

    Install

    npm install style-loader --save-dev

    Usage

    It's recommended to combine style-loader with the css-loader

    component.js

    import style from './file.css'

    webpack.config.js

    {
      module: {
        rules: [
          {
            test: /\.css$/,
            use: [
              { loader: "style-loader" },
              { loader: "css-loader" }
            ]
          }
        ]
      }
    }

    Locals (CSS Modules)

    When using local scoped CSS the module exports the generated identifiers (locals).

    component.js

    import style from './file.css'
    
    style.className === "z849f98ca812"

    Url

    It's also possible to add a URL <link href="path/to/file.css" rel="stylesheet"> instead of inlining the CSS {String} with <style></style> tag.

    import url from 'file.css'

    webpack.config.js

    {
      module: {
        rules: [
          {
            test: /\.css$/,
            use: [
              { loader: "style-loader/url" },
              { loader: "file-loader" }
            ]
          }
        ]
      }
    }
    <link rel="stylesheet" href="path/to/file.css">

    ℹ️ Source maps and assets referenced with url: when style loader is used with { options: { sourceMap: true } } option, the CSS modules will be generated as Blobs, so relative paths don't work (they would be relative to chrome:blob or chrome:devtools). In order for assets to maintain correct paths setting output.publicPath property of webpack configuration must be set, so that absolute paths are generated. Alternatively you can enable the convertToAbsoluteUrls option mentioned above.

    Useable

    By convention the Reference Counter API should be bound to .useable.css and the .css should be loaded with basic style-loader usage.(similar to other file types, i.e. .useable.less and .less).

    webpack.config.js

    {
      module: {
        rules: [
          {
            test: /\.css$/,
            use: [
              { loader: "style-loader" },
              { loader: "css-loader" },
            ],
          },
          {
            test: /\.useable\.css$/,
            use: [
              {
                loader: "style-loader/useable"
              },
              { loader: "css-loader" },
            ],
          },
        ],
      },
    }

    Reference Counter API

    component.js

    import style from './file.css'
    
    style.use(); // = style.ref();
    style.unuse(); // = style.unref();

    Styles are not added on import/require(), but instead on call to use/ref. Styles are removed from page if unuse/unref is called exactly as often as use/ref.

    ⚠️ Behavior is undefined when unuse/unref is called more often than use/ref. Don't do that.

    Options

    Name Type Default Description
    hmr {Boolean} true Enable/disable Hot Module Replacement (HMR), if disabled no HMR Code will be added (good for non local development/production)
    base {Number} true Set module ID base (DLLPlugin)
    attrs {Object} {} Add custom attrs to <style></style>
    transform {Function} false Transform/Conditionally load CSS by passing a transform/condition function
    insertAt {String|Object} bottom Inserts <style></style> at the given position
    insertInto {String|Function} <head> Inserts <style></style> into the given position
    singleton {Boolean} undefined Reuses a single <style></style> element, instead of adding/removing individual elements for each required module.
    sourceMap {Boolean} false Enable/Disable Sourcemaps
    convertToAbsoluteUrls {Boolean} false Converts relative URLs to absolute urls, when source maps are enabled

    hmr

    Enable/disable Hot Module Replacement (HMR), if disabled no HMR Code will be added. This could be used for non local development and production.

    webpack.config.js

    {
      loader: 'style-loader',
      options: {
        hmr: false
      }
    }

    base

    This setting is primarily used as a workaround for css clashes when using one or more DllPlugin's. base allows you to prevent either the app's css (or DllPlugin2's css) from overwriting DllPlugin1's css by specifying a css module id base which is greater than the range used by DllPlugin1 e.g.:

    webpack.dll1.config.js

    {
      test: /\.css$/,
      use: [
        'style-loader',
        'css-loader'
      ]
    }

    webpack.dll2.config.js

    {
      test: /\.css$/,
      use: [
        { loader: 'style-loader', options: { base: 1000 } },
        'css-loader'
      ]
    }

    webpack.app.config.js

    {
      test: /\.css$/,
      use: [
        { loader: 'style-loader', options: { base: 2000 } },
        'css-loader'
      ]
    }
    

    attrs

    If defined, style-loader will attach given attributes with their values on <style> / <link> element.

    component.js

    import style from './file.css'

    webpack.config.js

    {
      test: /\.css$/,
      use: [
        { loader: 'style-loader', options: { attrs: { id: 'id' } } }
        { loader: 'css-loader' }
      ]
    }
    <style id="id"></style>

    Url

    component.js

    import link from './file.css'

    webpack.config.js

    {
      test: /\.css$/,
      use: [
        { loader: 'style-loader/url', options: { attrs: { id: 'id' } } }
        { loader: 'file-loader' }
      ]
    }

    transform

    A transform is a function that can modify the css just before it is loaded into the page by the style-loader. This function will be called on the css that is about to be loaded and the return value of the function will be loaded into the page instead of the original css. If the return value of the transform function is falsy, the css will not be loaded into the page at all.

    webpack.config.js

    {
      loader: 'style-loader',
      options: {
        transform: 'path/to/transform.js'
      }
    }

    transform.js

    module.exports = function (css) {
      // Here we can change the original css
      const transformed = css.replace('.classNameA', '.classNameB')
    
      return transformed
    }

    Conditional

    webpack.config.js

    {
      loader: 'style-loader',
      options: {
        transform: 'path/to/conditional.js'
      }
    }

    conditional.js

    module.exports = function (css) {
      // If the condition is matched load [and transform] the CSS
      if (css.includes('something I want to check')) {
        return css;
      }
      // If a falsy value is returned, the CSS won't be loaded
      return false
    }

    insertAt

    By default, the style-loader appends <style> elements to the end of the style target, which is the <head> tag of the page unless specified by insertInto. This will cause CSS created by the loader to take priority over CSS already present in the target. To insert style elements at the beginning of the target, set this query parameter to 'top', e.g

    webpack.config.js

    {
      loader: 'style-loader',
      options: {
        insertAt: 'top'
      }
    }

    A new <style> element can be inserted before a specific element by passing an object, e.g.

    webpack.config.js

    {
      loader: 'style-loader',
      options: {
        insertAt: {
            before: '#id'
        }
      }
    }

    insertInto

    By default, the style-loader inserts the <style> elements into the <head> tag of the page. If you want the tags to be inserted somewhere else you can specify a CSS selector for that element here. If you target an IFrame make sure you have sufficient access rights, the styles will be injected into the content document head.

    You can also pass function to override default behavior and insert styles in your container, e.g

    webpack.config.js

    {
      loader: 'style-loader',
      options: {
        insertInto: () => document.querySelector("#root"),
      }
    }

    Using function you can insert the styles into a ShadowRoot, e.g

    webpack.config.js

    {
      loader: 'style-loader',
      options: {
        insertInto: () => document.querySelector("#root").shadowRoot,
      }
    }

    singleton

    If defined, the style-loader will reuse a single <style></style> element, instead of adding/removing individual elements for each required module.

    ℹ️ This option is on by default in IE9, which has strict limitations on the number of style tags allowed on a page. You can enable or disable it with the singleton option.

    webpack.config.js

    {
      loader: 'style-loader',
      options: {
        singleton: true
      }
    }

    sourceMap

    Enable/Disable source map loading

    webpack.config.js

    {
      loader: 'style-loader',
      options: {
        sourceMap: true
      }
    }

    convertToAbsoluteUrls

    If convertToAbsoluteUrls and sourceMaps are both enabled, relative urls will be converted to absolute urls right before the css is injected into the page. This resolves an issue where relative resources fail to load when source maps are enabled. You can enable it with the convertToAbsoluteUrls option.

    webpack.config.js

    {
      loader: 'style-loader',
      options: {
        sourceMap: true,
        convertToAbsoluteUrls: true
      }
    }

    Maintainers

    Juho Vepsäläinen Joshua Wiens Artem Sapegin Michael Ciniawsky Alexander Krasnoyarov
    Tobias Koppers Kees Kluskens

    Keywords

    none

    Install

    npm i @vtex/style-loader

    DownloadsWeekly Downloads

    3

    Version

    0.21.1

    License

    MIT

    Unpacked Size

    43.6 kB

    Total Files

    11

    Last publish

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