jsxstyle-loader v1.1.1
jsxstyle-loader
jsxstyle-loader
is a webpack loader that extracts static style props from jsxstyle components into a separate CSS file.
Don’t know what jsxstyle is? Check out the jsxstyle README for more information.
Getting Started
Add a new rule object for
jsxstyle-loader
to your webpack config, below any other JS loaders.jsxstyle-loader
relies on untranspiled JSX to be present in order to extract styles. Since webpack loaders run from right to left and bottom to top,jsxstyle-loader
should be placed at the end of your list of JS loaders.Add
jsxstyle-loader
’s companion plugin to theplugins
section of your webpack config.Ensure your webpack config contains a loader that handles
.css
files.
When you’re done, the relevant parts of your webpack config should look like this:
const JsxstyleLoaderPlugin = require('jsxstyle-loader/plugin');
module.exports = {
// ...
plugins: [new JsxstyleLoaderPlugin()],
// ...
module: {
rules: [
// ...
{
test: /\.js$/,
use: [
// any loaders that transpile JSX should go above jsxstyle-loader
{
loader: 'your-cool-js-loader',
},
// jsxstyle-loader goes at the end
{
loader: 'jsxstyle-loader',
},
],
},
{
test: /\.css$/,
use: 'your-cool-css-loader',
},
// ...
],
},
};
Loader Options
styleGroups
By default, jsxstyle-loader
will extract all static style props on a jsxstyle component into one class. This can lead to CSS classes that contain a lot of common style declarations. A good CSS minifier should help with this, but if you want a bit more control over how styles are grouped into CSS classes, you can provide an array of CSS style objects. When jsxstyle-loader
encounters a component that contains all styles in a style object, those styles will be extracted into a separate class name.
For example, with the following loader config:
{
loader: 'jsxstyle-loader',
options: {
styleGroups: [
{
display: 'block',
},
{
marginLeft: 15,
marginRight: 15,
},
],
},
}
...and a jsxstyle component that looks like this:
import { Block } from 'jsxstyle';
<Block backgroundColor="blue" marginLeft={15} marginRight={15} padding={20} />;
...the styles on this component will be extracted into three separate classes:
._x0 {
display: block;
}
._x1 {
margin-left: 15px;
margin-right: 15px;
}
._x2 {
background-color: blue;
padding: 20px;
}
Without the styleGroups
parameter, all five style props would be extracted into one class.
namedStyleGroups
The namedStyleGroups
config option is just like the styleGroups
config option, with one key difference: it is expected to be an object of CSS style objects, not an array. The key of the CSS style object will be used as the class name if all props and values are present on a jsxstyle component.
whitelistedModules
The whitelistedModules
config option allows you to add modules to the evaluation context. For example, with the following loader config, any prop on a jsxstyle component that references a value from ./LayoutConstants.js
will be assumed to be evaluatable:
{
loader: 'jsxstyle-loader',
options: {
whitelistedModules: [
require.resolve('./LayoutConstants'),
],
},
}
Note: the modules you specify as
whitelistedModules
will not be transpiled, so make sure they’re in a format that’s compatible with your version of node.
parserPlugins
jsxstyle-loader
uses babylon
to parse javascript into an AST. By default, jsxstyle-loader
is preconfigured with most of babylon
’s plugins enabled, but if you need to enable additional plugins, you can specify an array of plugins with the parserPlugins
option.
You can see a list of all available plugins in the babylon
README.
classNameFormat
Out of the box, jsxstyle-loader
will use a non-deterministic class naming scheme. Because webpack’s module iteration order is not guaranteed, class names will differ slightly between builds of the same code. If you need class names to remain the same each time the same code is bundled, set the classNameFormat
option to hash
in your loader config. Class names will be generated using a content-based hash.
liteMode
// look ma, no jsxstyle import
<block color="red">This text will be red</block>
Instead of importing components from jsxstyle
or jsxstyle/preact
, don’t import anything and just use the dash-case version of the component name as if it’s a valid DOM element. When jsxstyle-loader
encounters one of these dash-case elements, it’ll treat it like the PascalCased equivalent component imported from jsxstyle
or jsxstyle/preact
.
To enable this feature, set liteMode
in your loader options to either 'react'
or 'preact'
.
FAQs
Can I use jsxstyle-loader
with Flow?
Yes! Flow parsing is automatically enabled for any non-Typescript files.
Can I use jsxstyle-loader
with Typescript?
Yes! Take a look at the TypeScript example and issue #82 for some context. You’ll need to make a few configuration changes:
- Set
jsx
topreserve
in thecompilerOptions
section of yourtsconfig.json
file. - Ensure
jsxstyle-loader
runs afterts-loader
. Webpack loaders run from bottom to top, tojsxstyle-loader
needs to be placed beforets-loader
in your webpack config. - Add a loader that transpiles JSX, since
ts-loader
is now set to preserve JSX.
It’s not working 😩
- Make sure the loader object
test
regex matches JS files that use jsxstyle. jsxstyle-loader
relies on JSX still being around, so make sure it runs beforebabel-loader
does its thing.jsxstyle-loader
only supports destructuredrequire
/import
syntax:// Cool! import { Block } from 'jsxstyle'; <Block />; // Neat! const { Block } = require('jsxstyle'); <Block />; // Nope :( const Block = require('jsxstyle').Block; <Block />;
What are “static style props”?
Simply put, static style props are props whose values can be evaluated at build time. By default, this consists of any literal type (string
, number
, null
) as well as any variables provided to the evaluation context. The evaluation context is derived from the prop’s current scope.
For example, the fontSize
prop in the following component will be marked as evaluatable and will be extracted as 42
:
import { Block } from 'jsxstyle';
const bestNumber = 42;
<Block fontSize={bestNumber}>hello</Block>;
Any modules marked as whitelisted with the whitelistedModules
config option will also be added to the evaluation context.
If the value of a style prop is a ternary and both sides can be evaluated, the prop will be extracted and the ternary condition will be moved to the className
.
If the value of a prop is a simple logical expression with the &&
operator, it will be converted to a ternary with a null alternate.
Inline styles… are bad.
See the jsxstyle FAQs.
Does it work with hot reloading?
It sure does, but using it in development will only cause confusion, since what you will see in the developer tools is the transformed JS. jsxstyle-loader
is a production optimisation.
Any caveats?
One big one: CSS class names are not de-duplicated across components. Any CSS minifier that combines identical class names will handle deduplication.
Contributing
Got an idea for jsxstyle-loader
? Did you encounter a bug? Open an issue and let’s talk it through. PRs welcome too!
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