markdown-it-table-of-contents

A table of contents plugin for Markdown-it. Simple, customizable and with a default slugifier that matches that of https://www.npmjs.com/package/markdown-it-anchor (>5.0.0).

Usage

var MarkdownIt = require("markdown-it");
var md = new MarkdownIt();

md.use(require("markdown-it-anchor").default); // Optional, but makes sense as you really want to link to something, see info about recommended plugins below
md.use(require("markdown-it-table-of-contents"));

Then add [[toc]] where you want the table of contents to be added in your markdown.

Example markdown

This markdown:

# Heading

[[toc]]

## Sub heading 1
Some nice text

## Sub heading 2
Some even nicer text

... would render this HTML using the default options specified in "usage" above:

<h1 id="heading">Heading</h1>

<div class="table-of-contents">
  <ul>
    <li><a href="#heading">Heading</a>
      <ul>
        <li><a href="#sub-heading-1">Sub heading 1</a></li>
        <li><a href="#sub-heading-2">Sub heading 2</a></li>
      </ul>
    </li>
  </ul>
</div>

<h2 id="sub-heading-1">Sub heading 1</h2>
<p>Some nice text</p>

<h2 id="sub-heading-2">Sub heading 2</h2>
<p>Some even nicer text</p>

Options

You may specify options when useing the plugin. like so:

md.use(require("markdown-it-table-of-contents"), options);

These options are available:

Name	Description	Default
"includeLevel"	Headings levels to use (2 for h2:s etc)	[1, 2]
"containerClass"	The class for the container DIV	"table-of-contents"
"slugify"	A custom slugification function	encodeURIComponent(String(s).trim().toLowerCase().replace(/\s+/g, '-'))
"markerPattern"	Regex pattern of the marker to be replaced with TOC	/^\[\[toc\]\]/im
"listType"	Type of list (ul for unordered, ol for ordered)	ul
"format"	A function for formatting headings (see below)	md.renderInline(content)
"containerHeaderHtml"	Optional HTML string for container header	<div class="toc-container-header">Contents</div>
"containerFooterHtml"	Optional HTML string for container footer	<div class="toc-container-footer">Footer</div>
"transformLink"	A function for transforming the TOC links	undefined

format is an optional function for changing how the headings are displayed in the TOC.

By default, TOC headings will be formatted using markdown-it's internal MD formatting rules (i.e. it will be formatted using the same rules / extensions as other markdown in your document). You can override this behavior by specifying a custom format function. The function should accept two arguments:

1. content - The heading test, as a markdown string.
2. md – markdown-it's internal markdown parser object. This should only be need for advanced use cases.

function format(content, md) {
  // manipulate the headings as you like here.
  return manipulatedHeadingString;
}

transformLink is an optional function for transform the link as you like.

function transformLink(link) {
  // transform the link as you like here.
  return transformedLink;
}

Recommended plugins

By default, markdown-it-table-of-contents collects all headings and renders a nested list. It uses the slugify() function to create anchor targets for the links in the list. However, the headlines in your markdown document are not touched by markdown-it-table-of-contents. You'd have a nice table of contents, but the links don't link to anything. That's why you need another plugin to generate ids (anchor link targets) for all of your headlines. There are two recommended plugins to achieve this:

markdown-it-anchor

This plugin transforms all headlines in a markdown document so that the HTML code includes an id. It slugifies the headline:

## Hello world, I think you should read this article

Becomes

<h2 id="hello-world-i-think-you-should-read-this-article">Hello world</h2>

markdown-it-attrs

This plugin lets you attach custom attributes to your headlines. This is especially useful, if you have long headlines but want short anchors:

## Hello world, I think you should read this article {#hello}

Becomes

<h2 id="hello">Hello world, I think you should read this article</h2>

Full example with unusual headline order

Of course, both plugins can be combined. markdown-it-anchor ignores headlines that already have an id attribute.

Furthermore, markdown-it-table-of-contents can handle unusual heading orders. Consider the full example below:

var md = new MarkdownIt();
md.use(markdownItTOC, {
  "includeLevel": [2,3,4]
});
md.use(require("markdown-it-attrs"));
md.use(require("markdown-it-anchor"));

# Article

[[toc]]

### A message from our sponsors

Ad

## Hello world, I think you should read this article {#hello}

Lorem ipsum

## What's next?

Read this next...

#### See related articles {#related}

HTML output:

<h1 id="article">Article</h1>
<p>
    <div class="table-of-contents">
        <ul>
            <li>
                <ul>
                    <li><a href="#a-message-from-our-sponsors">A message from our sponsors</a></li>
                </ul>
            </li>
            <li><a href="#hello">Hello world, I think you should read this article</a></li>
            <li><a href="#what's-next%3F">What's next?</a>
                <ul>
                    <li>
                        <ul>
                            <li><a href="#related">See related articles</a></li>
                        </ul>
                    </li>
                </ul>
            </li>
        </ul>
    </div>
</p>
<h3 id="a-message-from-our-sponsors">A message from our sponsors</h3>
<p>Ad</p>
<h2 id="hello">Hello world, I think you should read this article</h2>
<p>Lorem ipsum</p>
<h2 id="what's-next%3F">What's next?</h2>
<p>Read this next...</p>
<h4 id="related">See related articles</h4>

Additional infos

• This plugin outputs a semantically correct table of contents. Sub-lists are rendered within the parent <li> tag and not as a separate (empty) <li>.
• Headlines can be in an arbitrary order. For example, h3, h2, h4. Please note that the jump from h2 to h4 causes a doube-indentation, which is correct.