eleventy-plugin-bundle

Little bundles of code, little bundles of joy.

Create minimal per-page or app-level bundles of CSS, JavaScript, or HTML to be included in your Eleventy project.

Makes it easy to implement Critical CSS, in-use-only CSS/JS bundles, SVG icon libraries, or secondary HTML content to load via XHR.

Why?

This project is a minimum-viable-bundler and asset pipeline in Eleventy. It does not perform any transpilation or code manipulation (by default). The code you put in is the code you get out (with configurable transforms if you’d like to modify the code).

For more larger, more complex use cases you may want to use a more full featured bundler like Vite, Parcel, Webpack, rollup, esbuild, or others.

But do note that a full-featured bundler has a significant build performance cost, so take care to weigh the cost of using that style of bundler against whether or not this plugin has sufficient functionality for your use case—especially as the platform matures and we see diminishing returns on code transpilation (ES modules everywhere).

Installation

It’s available on npm as @11ty/eleventy-plugin-bundle:

npm install @11ty/eleventy-plugin-bundle

And then in your Eleventy configuration file (probably .eleventy.js):

const bundlerPlugin = require("@11ty/eleventy-plugin-bundle");

module.exports = function(eleventyConfig) {
	eleventyConfig.addPlugin(bundlerPlugin);
};

Full options list

And then in your Eleventy configuration file (probably .eleventy.js):

const bundlerPlugin = require("@11ty/eleventy-plugin-bundle");

module.exports = function(eleventyConfig) {
	eleventyConfig.addPlugin(bundlerPlugin, {
		// Folder (in the output directory) bundle files will write to:
		toFileDirectory: "bundle",

		// Extra bundle names ("css", "js", "html" are guaranteed)
		bundles: [],

		// Array of async-friendly callbacks to transform bundle content.
		// Works with getBundle and getBundleFileUrl
		transforms: [],

		// Array of bundle names eligible for duplicate bundle hoisting
		hoistDuplicateBundlesFor: [], // e.g. ["css", "js"]
	});
};

Read more about hoistDuplicateBundlesFor and duplicate bundle hoisting.

Usage

The following Universal Shortcodes (available in njk, liquid, hbs, 11ty.js, and webc) are provided by this plugin:

css, js, and html to add code to a bundle.
getBundle and getBundleFileUrl to get bundled code.

Here’s a real-world commit showing this in use on the eleventy-base-blog project.

Add bundle code in a Markdown file in Eleventy

# My Blog Post

This is some content, I am writing markup.

{% css %}
em { font-style: italic; }
{% endcss %}

## More Markdown

{% css %}
strong { font-weight: bold; }
{% endcss %}

Renders to:

<h1>My Blog Post</h1>

<p>This is some content, I am writing markup.</p>

<h2>More Markdown</h2>

Note that the bundled code is excluded!

Render bundle code

<!-- Use this *anywhere*: a layout file, content template, etc -->
<style>{% getBundle "css" %}</style>

<!--
You can add more code to the bundle after calling
getBundle and it will be included.
-->
{% css %}* { color: orange; }{% endcss %}

Write a bundle to a file

Writes the bundle content to a content-hashed file location in your output directory and returns the URL to the file for use like this:

<link rel="stylesheet" href="{% getBundleFileUrl "css" %}">

Note that writing bundles to files will likely be slower for empty-cache first time visitors but better cached in the browser for repeat-views (and across multiple pages, too).

Asset bucketing

<!-- This goes into a `defer` bucket (the bucket can be any string value) -->
{% css "defer" %}em { font-style: italic; }{% endcss %}

<!-- Pass the arbitrary `defer` bucket name as an additional argument -->
<style>{% getBundle "css", "defer" %}</style>
<link rel="stylesheet" href="{% getBundleFileUrl 'css', 'defer' %}">

A default bucket is implied:

<!-- These two statements are the same -->
{% css %}em { font-style: italic; }{% endcss %}
{% css "default" %}em { font-style: italic; }{% endcss %}

<!-- These two are the same too -->
<style>{% getBundle "css" %}</style>
<style>{% getBundle "css", "default" %}</style>

Examples

Critical CSS

Use asset bucketing to divide CSS between the default bucket and a defer bucket, loaded asynchronously.

(Note that some HTML boilerplate has been omitted from the sample below)

<!-- … -->
<head>
	<!-- Inlined critical styles -->
	<style>{% getBundle "css" %}</style>

	<!-- Deferred non-critical styles -->
	<link rel="stylesheet" href="{% getBundleFileUrl 'css', 'defer' %}" media="print" onload="this.media='all'">
	<noscript>
		<link rel="stylesheet" href="{% getBundleFileUrl 'css', 'defer' %}">
	</noscript>
</head>
<body>
	<!-- This goes into a `default` bucket -->
	{% css %}/* Inline in the head, great with @font-face! */{% endcss %}
	<!-- This goes into a `defer` bucket (the bucket can be any string value) -->
	{% css "defer" %}/* Load me later */{% endcss %}
</body>
<!-- … -->

Related:

Check out the demo of Critical CSS using Eleventy Edge for a repeat view optimization without JavaScript.
You may want to improve the above code with fetchpriority when browser support improves.

SVG Icon Library

Here svg is an asset bucket on the html bundle.

<svg width="0" height="0" aria-hidden="true" style="position: absolute;">
	<defs>{% getBundle "html", "svg" %}</defs>
</svg>

<!-- And anywhere on your page you can add icons to the set -->
{% html "svg" %}
<g id="icon-close"><path d="…" /></g>
{% endhtml %}

And now you can use `icon-close` in as many SVG instances as you’d like (without repeating the heftier SVG content).

<svg><use xlink:href="#icon-close"></use></svg>
<svg><use xlink:href="#icon-close"></use></svg>
<svg><use xlink:href="#icon-close"></use></svg>
<svg><use xlink:href="#icon-close"></use></svg>

React Helmet-style `<head>` additions

This might exist in an Eleventy layout file:

<head>
	{% getBundle "html", "head" %}
</head>

And then in your content you might want to page-specific preconnect:

{% html "head" %}
<link href="https://v1.opengraph.11ty.dev" rel="preconnect" crossorigin>
{% endhtml %}

Bundle Sass with the Render Plugin

You can render template syntax inside of the {% css %} shortcode too, if you’d like to do more advanced things using Eleventy template types.

This example assumes you have added the Render plugin and the scss custom template type to your Eleventy configuration file.

{% css %}
  {% renderTemplate "scss" %}
  h1 { .test { color: red; } }
  {% endrenderTemplate %}
{% endcss %}

Now the compiled Sass is available in your default bundle and will show up in getBundle and getBundleFileUrl.

Use with WebC

Starting with @11ty/eleventy-plugin-webc@0.9.0 (track at issue #48) this plugin is used by default in the Eleventy WebC plugin. Specifically, WebC Bundler Mode now uses the bundle plugin under the hood.

To add CSS to a bundle in WebC, you would use a <style> element in a WebC page or component:

<style>/* This is bundled. */</style>
<style webc:keep>/* Do not bundle me—leave as is */</style>

To add JS to a page bundle in WebC, you would use a <script> element in a WebC page or component:

<script>/* This is bundled. */</script>
<script webc:keep>/* Do not bundle me—leave as is */</script>

Existing calls via WebC helpers getCss or getJs (e.g. <style @raw="getCss(page.url)">) have been wired up to getBundle (for "css" and "js" respectively) automatically.
- For consistency, you may prefer using the bundle plugin method names everywhere: <style @raw="getBundle('css')"> and <script @raw="getBundle('js')"> both work fine.
Outside of WebC, the Universal Filters webcGetCss and webcGetJs were available to access CSS and JS bundles but are considered deprecated in favor of the getBundle Universal Shortcode ({% getBundle "css" %} and {% getBundle "js" %} respectively).

Modify the bundle output

You can wire up your own async-friendly callbacks to transform the bundle output too. Here’s a quick example of postcss integration.

const bundlerPlugin = require("@11ty/eleventy-plugin-bundle");
const postcss = require("postcss");
const postcssNested = require("postcss-nested");

module.exports = function(eleventyConfig) {
	eleventyConfig.addPlugin(bundlerPlugin, {
		transforms: [
			async function(content) {
				// this.type returns the bundle name.
				if (this.type === 'css') {
					// Same as Eleventy transforms, this.page is available here.
					let result = await postcss([postcssNested]).process(content, { from: this.page.inputPath, to: null });
					return result.css;
				}

				return content;
			}
		]
	});
};

Bundling on the Edge

Coming soon

Advanced options:

Add your own bundle type

If you’d like to add your own bundle types (in addition to the guaranteed types: css, js, and html), you can do so:

const bundlerPlugin = require("@11ty/eleventy-plugin-bundle");

module.exports = function(eleventyConfig) {
	eleventyConfig.addPlugin(bundlerPlugin, {
		bundles: ["possum"]
	});
};

This does two things:

creates a new possum shortcode for adding arbitrary code to this bundle
adds "possum" as an eligible type argument to getBundle and getBundleFileUrl

Limitations

Bundles do not support nesting or recursion (yet?). If this will be useful to you, please file an issue!

ashur/eleventy-plugin-bundle

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