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Author message:

broken, use 1.0.0-rc.3 or higher

jsxstyle-loader
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1.0.0-rc.2 • Public • Published

jsxstyle-loader

jsxstyle-loader is a webpack loader that extracts static style props from jsxstyle components into a separate CSS file.

Getting Started

Just three easy steps™:

  1. Add a new rule object for jsxstyle-loader to your webpack config.

  2. Add a loader that handles .css files to your webpack config, because jsxstyle-loader adds a .css require to each component that uses jsxstyle.

  3. Add jsxstyle-loader’s companion plugin to the plugins section of your webpack config.

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$/,
        use: 'jsxstyle-loader',
      },
      {
        test: /\.css$/,
        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 extracted style props would be in 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'),
    ],
  },
}
// ...

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.

FAQs probably

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! Typescript parsing is automatically enabled for .ts and .tsx files, but if you’re using a different file extension, you’ll need to manually add typescript to the parserPlugins array.

It’s not working 😩

  1. Make sure the loader object test regex matches JS files that use jsxstyle.
  2. jsxstyle-loader relies on JSX still being around, so make sure it runs before babel-loader does its thing.
  3. jsxstyle-loader only supports destructured require/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 README.

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 for now: CSS class names are not de-duplicated. It’s a feature I’d like to add before 1.0, but for now, I recommend using postcss-loader with the postcss-discard-duplicates plugin.


⚠️ Experimental ⚠️

jsxstyle lite

This is a smokey the bear “leave no trace” type of deal right here. In your components, require from jsxstyle/lite instead of jsxstyle or jsxstyle/lite/preact instead of jsxstyle/preact. jsxstyle-loader will still extract every style it can, but dynamic styles will be ignored (with a warning) and all traces of runtime jsxstyle will be removed. WhoOOOoAoOA thAT’s CRAzyy.

jsxstyle even lite-r

Close your eyes for a second and imagine with me… imagine if you didn’t even have to require jsxstyle to use it. Just think… all those dozens of characters you don’t have to type anymore.

Ok, now open your eyes and then lay them upon this piece of JSX:

// 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/lite.

To enable this feature, pass an options object to JsxstyleLoaderPlugin with the __experimental__extremelyLiteMode key set to either "react" or "preact".

Stylesheet aggregation

By default, jsxstyle-loader adds one stylesheet for each component that uses jsxstyle. It’s nice for debugging and tends to work well for small to medium projects (i.e. < 100 components that use jsxstyle). However, if you’ve got hundreds of components that use jsxstyle and you use css-loader on all those extracted stylesheets, you’ll end up with hundreds of elements added to your document head on page load. Maybe that’s not your style. Pass an object to JsxstyleLoaderPlugin with the __experimental__combineCSS set to true and jsxstyle-loader smash all those MF stylesheets into one megastylesheet.

Shhhh don’t tell anyone but it’ll also rewrite relative url() paths to point to the right thing. “But why would I want to use relative paths?”, you say. Well, combine an extracted stylesheet with css-loader and you’ve got the full power of webpack require() in any CSS prop that uses a URL:

<Block backgroundImage="url(!!cool-base64-loader!./path/to/an.svg)" />

Ideally this would only be a feature in jsxstyle/lite since the runtime version of jsxstyle (obviously) doesn’t support this feature. That’s why it’s experimental.

Keywords

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Install

npm i [email protected]

Version

1.0.0-rc.2

License

Apache-2.0

Last publish

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