fis-msprd-css-loader_0_26_1
v0.26.1
Published
css loader module for webpack
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css loader for webpack
installation
npm install css-loader --save-dev
Usage
var css = require("css-loader!./file.css");
// => returns css code from file.css, resolves imports and url(...)
@import
and url(...)
are interpreted like require()
and will be resolved by the css-loader.
Good loaders for requiring your assets are the file-loader
and the url-loader which you should specify in your config (see below).
To be compatible with existing css files (if not in CSS Module mode):
url(image.png)
=>require("./image.png")
url(~module/image.png)
=>require("module/image.png")
Example config
This webpack config can load css files, embed small png images as Data Urls and jpg images as files.
module.exports = {
module: {
loaders: [
{ test: /\.css$/, loader: "style-loader!css-loader" },
{ test: /\.png$/, loader: "url-loader?limit=100000" },
{ test: /\.jpg$/, loader: "file-loader" }
]
}
};
'Root-relative' urls
For urls that start with a /
, the default behavior is to not translate them:
url(/image.png)
=>url(/image.png)
If a root
query parameter is set, however, it will be prepended to the url
and then translated:
With a config like:
loaders: [
{ test: /\.css$/, loader: "style-loader!css-loader?root=." },
...
]
The result is:
url(/image.png)
=>require("./image.png")
Using 'Root-relative' urls is not recommended. You should only use it for legacy CSS files.
Local scope
By default CSS exports all class names into a global selector scope. Styles can be locally scoped to avoid globally scoping styles.
The syntax :local(.className)
can be used to declare className
in the local scope. The local identifiers are exported by the module.
With :local
(without brackets) local mode can be switched on for this selector. :global(.className)
can be used to declare an explicit global selector. With :global
(without brackets) global mode can be switched on for this selector.
The loader replaces local selectors with unique identifiers. The choosen unique identifiers are exported by the module.
Example:
:local(.className) { background: red; }
:local .className { color: green; }
:local(.className .subClass) { color: green; }
:local .className .subClass :global(.global-class-name) { color: blue; }
is transformed to
._23_aKvs-b8bW2Vg3fwHozO { background: red; }
._23_aKvs-b8bW2Vg3fwHozO { color: green; }
._23_aKvs-b8bW2Vg3fwHozO ._13LGdX8RMStbBE9w-t0gZ1 { color: green; }
._23_aKvs-b8bW2Vg3fwHozO ._13LGdX8RMStbBE9w-t0gZ1 .global-class-name { color: blue; }
and the identifiers are exported:
exports.locals = {
className: "_23_aKvs-b8bW2Vg3fwHozO",
subClass: "_13LGdX8RMStbBE9w-t0gZ1"
}
Camelcasing is recommended for local selectors. They are easier to use in the importing javascript module.
url(...)
URLs in block scoped (:local .abc
) rules behave like requests in modules:
./file.png
instead offile.png
module/file.png
instead of~module/file.png
You can use :local(#someId)
, but this is not recommended. Use classes instead of ids.
You can configure the generated ident with the localIdentName
query parameter (default [hash:base64]
). Example: css-loader?localIdentName=[path][name]---[local]---[hash:base64:5]
for easier debugging.
You can also specify the absolute path to your custom getLocalIdent
function to generate classname based on a different schema. Note that this requires webpack@2
since to be able to pass function in. For example:
{
test: /\.css$/,
loaders: [
{
loader: 'css-loader',
query: {
modules: true,
importLoaders: 1,
getLocalIdent: function (loaderContext, localIdentName, localName, options) {
return 'whatever_random_class_name'
}
}
}
]
},
Note: For prerendering with extract-text-webpack-plugin you should use css-loader/locals
instead of style-loader!css-loader
in the prerendering bundle. It doesn't embed CSS but only exports the identifier mappings.
CSS Modules
See CSS Modules.
The query parameter modules
enables the CSS Modules spec. (css-loader?modules
)
This enables Local scoped CSS by default. (You can switch it off with :global(...)
or :global
for selectors and/or rules.)
Composing CSS classes
When declaring a local class name you can compose a local class from another local class name.
:local(.className) {
background: red;
color: yellow;
}
:local(.subClass) {
composes: className;
background: blue;
}
This doesn't result in any change to the CSS itself but exports multiple class names:
exports.locals = {
className: "_23_aKvs-b8bW2Vg3fwHozO",
subClass: "_13LGdX8RMStbBE9w-t0gZ1 _23_aKvs-b8bW2Vg3fwHozO"
}
and CSS is transformed to:
._23_aKvs-b8bW2Vg3fwHozO {
background: red;
color: yellow;
}
._13LGdX8RMStbBE9w-t0gZ1 {
background: blue;
}
Importing local class names
To import a local class name from another module:
:local(.continueButton) {
composes: button from "library/button.css";
background: red;
}
:local(.nameEdit) {
composes: edit highlight from "./edit.css";
background: red;
}
To import from multiple modules use multiple composes:
rules.
:local(.className) {
composes: edit hightlight from "./edit.css";
composes: button from "module/button.css";
composes: classFromThisModule;
background: red;
}
SourceMaps
To include SourceMaps set the sourceMap
query param.
require("css-loader?sourceMap!./file.css")
I. e. the extract-text-webpack-plugin can handle them.
They are not enabled by default because they expose a runtime overhead and increase in bundle size (JS SourceMap do not). In addition to that relative paths are buggy and you need to use an absolute public path which include the server url.
importing and chained loaders
The query parameter importLoaders
allow to configure which loaders should be applied to @import
ed resources.
importLoaders
(int): That many loaders after the css-loader are used to import resources.
Examples:
require("style-loader!css-loader?importLoaders=1!postcss-loader!...")
// => imported resources are handled this way:
require("css-loader?importLoaders=1!postcss-loader!...")
require("style-loader!css-loader!stylus-loader!...")
// => imported resources are handled this way:
require("css-loader!...")
This may change in the future, when the module system (i. e. webpack) supports loader matching by origin.
Minification
By default the css-loader minimizes the css if specified by the module system.
In some cases the minification is destructive to the css, so you can provide some options to it. cssnano is used for minification and you find a list of options here. Just provide them as query parameter: i. e. require("css-loader?-colormin")
to disable making color values as small as possible.
You can also disable or enforce minification with the minimize
query parameter.
require("css-loader?minimize!./file.css")
(enforced)
require("css-loader?-minimize!./file.css")
(disabled)
Disable behavior
css-loader?-url
disables url(...)
handling.
css-loader?-import
disables @import
handling.
Camel case
By default, the exported JSON keys mirror the class names. If you want to camelize class names (useful in Javascript), pass the query parameter camelCase
to the loader.
Example:
css-loader?camelCase
Usage:
/* file.css */
.class-name { /* ... */ }
// javascript
require('file.css').className
License
MIT (http://www.opensource.org/licenses/mit-license.php)