Why load stylesheets asynchronously?
Referencing CSS stylesheets with link[rel=stylesheet]
or @import
causes browsers to delay page rendering while a stylesheet loads. When loading stylesheets that are not critical to the initial rendering of a page, this blocking behavior is undesirable. The new <link rel="preload">
standard enables us to load stylesheets asynchronously, without blocking rendering.
Install via npm
npm install --save-dev async-stylesheet-webpack-plugin
Usage
The plugin will update all your webpack
bundles stylesheets in the head using link
tags with rel="preload"
attribute.
Just add the plugin to your webpack
config as follows:
webpack.config.js
const HtmlWebpackPlugin = require('html-webpack-plugin')
const AsyncStylesheetWebpackPlugin = require('async-stylesheet-webpack-plugin');
module.exports = {
...
plugins: [
new HtmlWebpackPlugin(),
new AsyncStylesheetWebpackPlugin(),
...
]
}
This will generate a file dist/index.html
containing the following:
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Webpack App</title>
<link href="app.css" rel="preload" as="style" onload="this.onload=null;this.rel='stylesheet';">
<noscript><link href="app.css" rel="stylesheet"></noscript>
</head>
<body>
<script src="app.js"></script>
</body>
</html>
Options
You can pass a hash of configuration options to async-stylesheet-webpack-plugin
. Allowed values are as follows:
Name | Type | Default | Description |
---|
preloadPolyfill | {Boolean} | false | If true then enabled legacy browser support |
noscriptFallback | {Boolean} | true | If true then enabled fallback stylesheets loading without JavaScript |
chunks | {String[]} | null | Allows you to async load only some chunks |
excludeChunks | {String[]} | null | Allows you to skip async load some chunks |
Here's an example webpack
config illustrating how to use these options:
webpack.config.js
module.exports = {
...
plugins: [
new HtmlWebpackPlugin(),
new AsyncStylesheetWebpackPlugin({
preloadPolyfill: true,
noscriptFallback: true
}),
...
]
}
Legacy browser support
Preload polyfill
If preloadPolyfill
option is enabled (this option disabled by default) async-stylesheet-webpack-plugin
adding in HTML head
cssrelpreload.js provided by loadCSS.
This will generate a file dist/index.html
containing the following:
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Webpack App</title>
<script type="text/javascript"></script>
<link href="app.css" rel="preload" as="style" onload="this.onload=null;this.rel='stylesheet';">
<noscript><link href="app.css" rel="stylesheet"></noscript>
</head>
<body>
<script src="app.js"></script>
</body>
</html>
Without JavaScript
If noscriptFallback
option is enabled (this option enabled by default) async-stylesheet-webpack-plugin
adding in HTML head
noscript
tag with traditional stylesheet loading.
This will generate a file dist/index.html
containing the following:
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Webpack App</title>
<link href="app.css" rel="preload" as="style" onload="this.onload=null;this.rel='stylesheet';">
<noscript><link href="app.css" rel="stylesheet"></noscript>
</head>
<body>
<script src="app.js"></script>
</body>
</html>
If noscriptFallback
option is disabled async-stylesheet-webpack-plugin
only updated link
tags:
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Webpack App</title>
<link href="app.css" rel="preload" as="style" onload="this.onload=null;this.rel='stylesheet';">
</head>
<body>
<script src="app.js"></script>
</body>
</html>
Credit
- loadCSS - A function for loading CSS asynchronously;
- HTML Webpack Plugin - Simplifies creation of HTML files to serve your webpack bundles.
See also
Need a feature?
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