Easily generate a table of contents (TOC) for your Eleventy site, with easy configuration and customization.

HTML:

<h1>Hello, World</h1>
Lorem ipsum dolor sit amet, consectetur adipisicing elit.

<h2 id="greetings-from-mars">Greetings from Mars</h2>
Lorem ipsum dolor sit amet, consectetur adipisicing elit.

<h3 id="the-red-planet">The red planet</h3>
Lorem ipsum dolor sit amet, consectetur adipisicing elit.

<h2 id="greetings-from-pluto">Greetings from Pluto</h2>

Generated TOC:

• Greetings from Mars
  • The red planet
• Greetings from Pluto

<nav class="toc">
	<ol>
		<li><a href="#greetings-from-mars">Greetings from Mars</a></li>
		<ol>
			<li><a href="#the-red-planet">The red planet</a></li>
		</ol>
		<li><a href="#greetings-from-pluto">Greetings from Pluto</a></li>
	</ol>
</nav>

npm i @uncenter/eleventy-plugin-toc
pnpm add @uncenter/eleventy-plugin-toc
yarn add @uncenter/eleventy-plugin-toc
bun add @uncenter/eleventy-plugin-toc

Your heading elements will need to have id attributes on them, so that the table of contents can provide anchor links to them. Eleventy does not do this for you out of the box. You can use a plugin like markdown-it-anchor to add id attributes to the headings automatically (or a similar plugin for your Markdown engine of choice).

In your Eleventy config file (.eleventy.js, eleventy.config.js, or eleventy.config.cjs), add your heading plugin of choice. This example uses the aforementioned markdown-it-anchor plugin:

import markdownIt from 'markdown-it';
import markdownItAnchor from 'markdown-it-anchor';

export default function (eleventyConfig) {
	eleventyConfig.setLibrary('md', markdownIt().use(markdownItAnchor));
}

Then add the table of contents plugin:

import pluginTOC from '@uncenter/eleventy-plugin-toc';

export default function (eleventyConfig) {
	eleventyConfig.addPlugin(pluginTOC);
}

To use the table of contents in your templates, apply the toc filter to your template content:

<aside>
  {{ content | toc | safe }}
</aside>
<article>
  {{ content }}
</article>

You can override some of the options at the time that you call it, or all of them when you add it in your Eleventy config. All of the options will be merged together, with the options passed to the filter taking precedence over the options passed to the plugin (which take precedence over the defaults).

Override the defaults for your whole site (defaults are shown):

{
    tags: ["h2", "h3", "h4"], // tags (heading levels) to include
    ignoredHeadings: ["[data-toc-exclude]"], // headings to ignore (list of selectors)
    ignoredElements: [], // elements (within the headings) to ignore when generating the TOC (list of selectors)
    ul: false, // whether to a use a `ul` or `ol`
    inheritAttributes: false, // whether to inherit heading attributes to TOC links
    wrapper: function (toc) {
        // wrapper around the generated TOC
        return `<nav class="toc">${toc}</nav>`;
    },
}

Or override as it's being invoked:

<aside>
  {{ content | toc(tags=['h2', 'h3']) | safe }}
</aside>

If you have specific headings which you don't want to be included in the TOC, you can add one of the ignoredHeadings selectors to exclude these headings (defaults to the[data-toc-exclude] selector).

Set inheritAttributes to true to copy heading attributes to TOC links, or provide an array of attribute names (e.g. ['data-value']) to copy only specific ones.

One way to add this attribute is via the use of the markdown-it-attrs plugin:

## Heading {data-toc-exclude}

MIT