critical-style-loader
v2.0.0
Published
A webpack loader for rendering critical path CSS on the server with utilities to avoid client side style-loader style duplications.
Downloads
15
Readme
Critical Style Loader
Dynamically generate critical path css by gathering all imported CSS modules used during a SSR request. Obtain the resulting CSS as a string to be rendered by your server application to avoid FOUC in the client.
Includes utilities to avoid duplicated styles in the browser by filtering any style-loader handled CSS that has been pre-rendered as critical CSS.
Inspirations
- https://github.com/kriasoft/isomorphic-style-loader
- https://github.com/shuboc/critical-css-style-loader
Install
npm install critical-style-loader
Usage
webpack.server.js
module.exports = {
module: {
rules: [
{
test: /\.css$/,
use: [
{
loader: 'critical-style-loader',
},
{
loader: 'css-loader',
options: {
modules: true,
}
}
],
},
],
},
};webpack.client.js
module.exports = {
module: {
rules: [
{
test: /\.css$/,
use: [
{
loader: 'style-loader',
options: {
transform: 'node_modules/critical-style-loader/lib/filterCriticalCss.js',
},
},
{
loader: 'css-loader',
options: {
modules: true,
}
}
],
},
],
},
};server.js
import express from 'express';
import React from 'react';
import { renderToString } from 'react-dom/server';
import { StyleContext, CriticalCssBuilder } from 'critical-style-loader/lib';
import App from 'components/app';
const app = express();
// ... configure express
app.use((req, res) => {
const cssBuilder = new CriticalCssBuilder();
const html = renderToString(
<StyleContext.Provider value={cssBuilder.addCss}>
<App />
</StyleContext.Provider>
);
res.render('app', {
html,
criticalCss: cssBuilder.getCss(),
criticalCssMap: cssBuilder.getEncodedMap(),
});
});
app.listen();app.ejs
<!doctype html>
<html lang="en">
<head>
<style id="critical-css"><%- criticalCss %></style>
</head>
<body>
<div id="root"><%- html %></div>
<script id="preload">
<%- criticalCssMap %>;
</script>
</body>
</html>components/app.js
import React from 'react';
import { withStyles } from 'critical-style-loader/lib';
import styles from './app.css';
const App = () => (
<h1 style={styles.heading}>Hello World!</h1>
);
const wrapWithStyles = withStyles(styles);
export default wrapWithStyles(App);client.js
import React from 'react';
import ReactDOM from 'react-dom';
import App from './components/app';
ReactDOM.hydrate(
<App />,
document.getElementById('root')
);