Table of Contents plugin for Rehype

A rehype plugin that adds a table of contents (TOC) to the page

Features

Adds a <nav> and <ol> list outlining all headings on the page
Combine with rehype-slug to create links to each heading
Ignores headings outside of <main> if it exists
You can customize which headings are included (defaults to <h1> - <h6>)
You can customize the CSS classes on every TOC element
Hooks give you complete customization of the generated HTML

Example

input.html
Here’s the original HTML file. There are three levels of headings (<h1> - <h3>), and none of them have IDs.

<html>
  <body>
    <h1>Apple Pie Recipe</h1>
    <p>This is the world's best apple pie recipe...</p>

    <div>
      <h2>Filling</h2>
      <p>The filling is the best part...</p>

      <h3>Preparing the apples</h3>
      <p>Cut the apples into 1/4 inch slices...</p>

      <h3>Preparing the spice mix</h3>
      <p>In a mixing bowl, combine sugar, cinnamon...</p>
    </div>

    <div>
      <h2>Crust</h2>
      <p>How to make the perfect flaky crust...</p>

      <h3>Preparing the dough</h3>
      <p>Combine flour, sugar, salt...</p>

      <h3>The criss-cross top</h3>
      <p>Cut the top crust into 1/2 inch strips...</p>
    </div>
  </body>
</html>

example.js
This script reads the input.html file above writes the results to output.html (shown below). The script uses unified, rehype-parse, rehype-slug, and rehype-stringify.

const unified = require("unified");
const parse = require("rehype-parse");
const slug = require("rehype-slug");
const toc = require("@jsdevtools/rehype-toc");
const stringify = require("rehype-stringify");
const fs = require("fs");

async function example() {
  // Create a Rehype processor with the TOC plugin
  const processor = unified()
    .use(parse)
    .use(slug)
    .use(toc)
    .use(stringify);

  // Read the original HTML file
  let inputHTML = await fs.promises.readFile("input.html");

  // Process the HTML, adding heading IDs and Table of Contents
  let outputHTML = await processor.process(inputHTML);

  // Save the new HTML
  await fs.promises.writeFile("output.html", outputHTML);
}

output.html
Here’s the HTML that gets created by the above script. Notice that a table of contents has been added at the top of the <body>, with links to each of the headings on the page. The headings also now have IDs, thanks to rehype-slug.

<html>
  <body>
    <nav class="toc">
      <ol class="toc-level toc-level-1">
        <li class="toc-item toc-item-h1">
          <a class="toc-link toc-link-h1" href="#apple-pie-recipe">
            Apple Pie Recipe
          </a>

          <ol class="toc-level toc-level-2">
            <li class="toc-item toc-item-h2">
              <a class="toc-link toc-link-h2" href="#filling">
                Filling
              </a>

              <ol class="toc-level toc-level-3">
                <li class="toc-item toc-item-h3">
                  <a class="toc-link toc-link-h3" href="#preparing-the-apples">
                    Preparing the apples
                  </a>
                </li>
                <li class="toc-item toc-item-h3">
                  <a class="toc-link toc-link-h3" href="#preparing-the-spice-mix">
                    Preparing the spice mix
                  </a>
                </li>
              </ol>
            </li>

            <li class="toc-item toc-item-h2">
              <a class="toc-link toc-link-h2" href="#crust">
                Crust
              </a>

              <ol class="toc-level toc-level-3">
                <li class="toc-item toc-item-h3">
                  <a class="toc-link toc-link-h3" href="#preparing-the-dough">
                    Preparing the dough
                  </a>
                </li>
                <li class="toc-item toc-item-h3">
                  <a class="toc-link toc-link-h3" href="#the-criss-cross-top">
                    The criss-cross top
                  </a>
                </li>
              </ol>
            </li>
          </ol>
        </li>
      </ol>
    </nav>

    <h1 id="apple-pie-recipe">Apple Pie Recipe</h1>
    <p>This is the world's best apple pie recipe...</p>

    <div>
      <h2 id="filling">Filling</h2>
      <p>The filling is the best part...</p>

      <h3 id="preparing-the-apples">Preparing the apples</h3>
      <p>Cut the apples into 1/4 inch slices...</p>

      <h3 id="preparing-the-spice-mix">Preparing the spice mix</h3>
      <p>In a mixing bowl, combine sugar, cinnamon...</p>
    </div>

    <div>
      <h2 id="crust">Crust</h2>
      <p>How to make the perfect flaky crust...</p>

      <h3 id="preparing-the-dough">Preparing the dough</h3>
      <p>Combine flour, sugar, salt...</p>

      <h3 id="the-criss-cross-top">The criss-cross top</h3>
      <p>Cut the top crust into 1/2 inch strips...</p>
    </div>
  </body>
</html>

Installation

You can install Rehype TOC via npm.

npm install @jsdevtools/rehype-toc

You’ll probably want to install unified, rehype-parse, rehype-stringify, and rehype-slug as well.

npm install unified rehype-parse rehype-stringify rehype-slug

Usage

Using the Rehype TOC plugin requires an understanding of how to use Unified and Rehype. Here is an excelleng guide to learn the basics.

The Rehype TOC plugin works just like any other Rehype plugin. Pass it to the .use() method, optionally with an options object.

const unified = require("unified");
const toc = require("@jsdevtools/rehype-toc");

// Use the Rehype TOC plugin with its default options
unified().use(toc);

// Use the Rehype TOC plugin with custom options
unified().use(toc, {
  headings: ["h1", "h2"],     // Only include <h1> and <h2> headings in the TOC
  cssClasses: {
    toc: "page-outline",      // Change the CSS class for the TOC
    link: "page-link",        // Change the CSS class for links in the TOC
  }
});

Options

The Rehype TOC plugin supports the following options:

Option	Type	Default	Description
`nav`	boolean	true	Determines whether the table of contents is wrapped in a `<nav>` element.
`position`	string	“afterbegin”	The position at which the table of contents should be inserted, relative to the `<main>` or `<body>` element. Can be “beforebegin”, “afterbegin”, “beforeend”, or “afterend”. See the `insertAdjacentElement()` docs for an explanation of each value.
`headings`	array of strings	h1, h2, h3, h4, h5, h6	The HTML heading tags to include in the table of contents
`cssClasses.toc`	string	toc	The CSS class name for the top-level `<nav>` or `<ol>` element that contains the whole table of contents.
`cssClasses.list`	string	toc-level	The CSS class name for all `<ol>` elements in the table of contents, including the top-level one.
`cssClasses.listItem`	string	toc-item	The CSS class name for all `<li>` elements in the table of contents.
`cssClasses.link`	string	toc-link	The CSS class name for all `<a>` elements in the table of contents.
`customizeTOC`	function(toc)		Allows you to customize the table of contents before it is added to the page. The function receives the TOC node tree and can modify it in any way you want. Or you can return a new node tree to use instead. Or return `false` to prevent the the TOC from being added to the page.
`customizeTOCItem`	function(toc, heading)		Allows you to customize each item in the table of contents before it is added to the page. The function receives the TOC item’s node tree and the heading node that it refers to. You can modify the nodes in any way you want. Or you can return a new node tree to use instead. Or return `false` to prevent the the TOC from being added to the page.

Contributing

Contributions, enhancements, and bug-fixes are welcome! Open an issue on GitHub and submit a pull request.

Building

To build the project locally on your computer:

Clone this repo
git clone https://github.com/JS-DevTools/rehype-toc.git
Install dependencies
npm install
Build the code
npm run build
Run the tests
npm test

License

Rehype TOC is 100% free and open-source, under the MIT license. Use it however you want.

This package is Treeware. If you use it in production, then we ask that you buy the world a tree to thank us for our work. By contributing to the Treeware forest you’ll be creating employment for local families and restoring wildlife habitats.

Big Thanks To

Thanks to these awesome companies for their support of Open Source developers ❤