cmaasmarkdown-it-table-of-contents
A table of contents plugin for Markdown-it. Simple, customizable and with a default slugifier that matches that of markdown-it-anchor (>5.0.0).
Usage
CommonJS:
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"));ESM:
import MarkdownIt from 'markdown-it';
import MarkdownItTOC from 'markdown-it-table-of-contents';
const md = new MarkdownIt();
md.use(MarkdownItTOC);Then add [[toc]] where you want the table of contents to be added in your document.
Want to use a table of contents generator client-side in the browser? Try my <table-of-contents> webcomponent: table-of-contents-element on GitHub. Advantage: can use more sophisticated query selector and better support for HTML customization.
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 |
omitTag |
HTML comment tag to exclude next headline from TOC | <!-- omit from toc --> |
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 | undefined |
containerFooterHtml |
Optional HTML string for container footer | undefined |
transformLink |
A function for transforming the TOC links | undefined |
transformContainerOpen |
A function for transforming the container opening tag | (see source code) |
transformContainerClose |
A function for transforming the container closing tag | (see source code) |
getTokensText |
A function for extracting text from tokens for titles | (see source code) |
transformLink is an optional function to transform the link as you like.
function transformLink(link) {
// transform the link as you like here.
return transformedLink;
}transformContainerOpen and transformContainerClose can be used to replace the container element with one or several more like so:
md.use(markdownItTOC, {
transformContainerOpen: () => {
return '<nav class="my-toc"><button>Toggle</button><h3>Table of Contents</h3>';
},
transformContainerClose: () => {
return '</nav>';
}
});Advanced headline text extraction / manipulation:
By default (and for historical consistency), formatting in headlines is dropped. If you have this headline:
# Heading with *emphasis* and **bold** and `code` and it will be shown as
<li><a href="#heading-with-emphasis-and-bold-and-code-and">Heading with emphasis and bold and code and</a></li>in your TOC. Please note that the alt text of the image is dropped. That is because getTokensText filters for text and code_inline token types only.
If you want to keep formatting in headlines, you can provide a custom getTokensText function as an option:
md.use(markdownItTOC, {
getTokensText: (tokens, rawToken) => {
return rawToken.content;
},
slugify: (text, rawToken) => {
const s = rawToken.children.map(t => t.content).join('').trim();
return encodeURIComponent(String(s).trim().toLowerCase().replace(/\s+/g, '-'));
}
});The data flow is as follows: getTokensText extracts text from a headline and passes this as first param to slugify and format. By default, only text elements are extracted and formatting is lost. See the source code to understand how this is done. In the above example, getTokensText returns the raw Markdown content of the headline token. The default format function receives the raw Markdown as first param and uses md.renderInline(content) to keep the formatting. However, the default slugify doesn't drop weird characters. You either need to provide your own slugify function or use rawToken in slugify to filter for text elements only that serve as the slug. It is strongly recommended to use plugins like markdown-it-anchor that assign IDs to headlines so that you don't need to use slugify at all. If a headline already has an anchor element, slugify is never called.
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:
content- The heading text, as a markdown string.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;
}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 articleBecomes
<h2 id="hello-world-i-think-you-should-read-this-article">Hello world, I think you should read this article</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>Example for omitting headlines from the TOC
If you want to exclude single headlines, you can use a special HTML comment to omit the next headline from the TOC:
<!-- omit from toc -->
# TitleFor this to work, the HTML comment must come right in the line before the headline you want to exclude. Furthermore, you need to allow HTML in MarkdownIT:
const md = new MarkdownIt({ html: true });You can override the HTML comment by using the option omitTag as explained above. Both, the tag and the actual comment in the Markdown file are case-insensitive.
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.