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readme.md

rehype-github-heading

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rehype plugin to enhance headings.

Contents

What is this?

This plugin enhances headings by adding links from headings back to themselves. By default it appends markup for an anchor tag with a link icon that, with some CSS, can be displayed next to the heading, potentially on hover.

These links are markup specific to github.com that only work in files, not in comments.

This plugin is part of a monorepo rehype-github. See its readme for more info.

When should I use this?

You can use this plugin when you want to match how github.com works or when you want to build similar pipelines where you have relatively long documents and want users to be able to link to particular sections.

Install

This package is ESM only. In Node.js (version 16+), install with npm:

npm install rehype-github-heading

In Deno with esm.sh:

import rehypeGithubHeading from 'https://esm.sh/rehype-github-heading@1'

In browsers with esm.sh:

<script type="module">
  import rehypeGithubHeading from 'https://esm.sh/rehype-github-heading@1?bundle'
</script>

Use

Say our module example.js looks as follows:

import rehypeGithubHeading from 'rehype-github-heading'
import rehypeParse from 'rehype-parse'
import rehypeStringify from 'rehype-stringify'
import {unified} from 'unified'

const file = await unified()
  .use(rehypeParse, {fragment: true})
  .use(rehypeGithubHeading)
  .use(rehypeStringify)
  .process('<h1>Hi!</h1>')

console.log(String(file))

…now running node example.js yields:

<h1><a id="hi" class="anchor" aria-hidden="true" href="#hi"><svg class="octicon octicon-link" viewBox="0 0 16 16" version="1.1" width="16" height="16" aria-hidden="true"><path d="m7.775 3.275 1.25-1.25a3.5 3.5 0 1 1 4.95 4.95l-2.5 2.5a3.5 3.5 0 0 1-4.95 0 .751.751 0 0 1 .018-1.042.751.751 0 0 1 1.042-.018 1.998 1.998 0 0 0 2.83 0l2.5-2.5a2.002 2.002 0 0 0-2.83-2.83l-1.25 1.25a.751.751 0 0 1-1.042-.018.751.751 0 0 1-.018-1.042Zm-4.69 9.64a1.998 1.998 0 0 0 2.83 0l1.25-1.25a.751.751 0 0 1 1.042.018.751.751 0 0 1 .018 1.042l-1.25 1.25a3.5 3.5 0 1 1-4.95-4.95l2.5-2.5a3.5 3.5 0 0 1 4.95 0 .751.751 0 0 1-.018 1.042.751.751 0 0 1-1.042.018 1.998 1.998 0 0 0-2.83 0l-2.5 2.5a1.998 1.998 0 0 0 0 2.83Z"></path></svg></a>Hi!</h1>

API

This package exports the identifiers defaultBuild and defaultInclude. The default export is rehypeGithubHeading.

defaultBuild(id)

Make rich content to link to a heading like github.com.

Parameters
  • id (string) — ID corresponding to heading
Returns

Link with icon (Element).

defaultInclude

Elements to look for to link (Array<string>).

rehypeGithubHeading(options?)

Plugin to enhance headings.

Parameters
  • options (Options, optional) — configuration

Behavior

Where to add the new link to the existing heading (TypeScript type).

You can either prepend or append to the heading.

Type
type Behavior = 'append' | 'prepend'

Build

Make rich content to link to a heading (TypeScript type).

Parameters
  • id (string) — ID of heading
  • node (Element) — heading
Returns

Rich content (Array<ElementContent> or ElementContent).

Options

Configuration (TypeScript type).

Fields
  • behavior (Behavior, default: 'prepend') — where to add the new link to the existing heading
  • build (Build, default: defaultBuild) — make rich content to link to a heading
  • include (Array<string>, default: defaultInclude) — elements to link; the default behavior is to enhance h1, h2, h3, h4, h5, and h6

Bugs

GitHubs behavior for this is pretty good! The main problem is that their behavior isn’t accessible for folks that do not use a cursor.

Authoring

Just be careful that GitHub generates links to headings based on the text of the heading, and to make them unique, appends counters to duplicates. These counters are in the order the document was written, which means that if an author swaps sections around, the links will be swapped too. To solve this, it is recommended to use headings with unique text.

See § Writing on GitHub for more info.

HTML

The markup for links is:

<a id="xxx" class="anchor" aria-hidden="true" href="#xxx"><svg class="octicon octicon-link" viewBox="0 0 16 16" version="1.1" width="16" height="16" aria-hidden="true"><path d="m7.775 3.275 1.25-1.25a3.5 3.5 0 1 1 4.95 4.95l-2.5 2.5a3.5 3.5 0 0 1-4.95 0 .751.751 0 0 1 .018-1.042.751.751 0 0 1 1.042-.018 1.998 1.998 0 0 0 2.83 0l2.5-2.5a2.002 2.002 0 0 0-2.83-2.83l-1.25 1.25a.751.751 0 0 1-1.042-.018.751.751 0 0 1-.018-1.042Zm-4.69 9.64a1.998 1.998 0 0 0 2.83 0l1.25-1.25a.751.751 0 0 1 1.042.018.751.751 0 0 1 .018 1.042l-1.25 1.25a3.5 3.5 0 1 1-4.95-4.95l2.5-2.5a3.5 3.5 0 0 1 4.95 0 .751.751 0 0 1-.018 1.042.751.751 0 0 1-1.042.018 1.998 1.998 0 0 0-2.83 0l-2.5 2.5a1.998 1.998 0 0 0 0 2.83Z"></path></svg></a>

…where xxx is the slug generated from the heading text.

CSS

The following CSS is needed to make headings look like GitHub.

/* Default dark */
:root {
  --color-accent-fg: #2f81f7;
  --color-fg-default: #e6edf3;
}

a {
  color: var(--color-accent-fg);
  text-decoration: none;
}

.octicon {
  display: inline-block;
  fill: currentColor;
  overflow: visible;
  vertical-align: text-bottom;
}

.anchor {
  float: left;
  line-height: 1;
  padding-right: 4px;
  margin-left: -20px;
}

:is(h1, h2, h3, h4, h5, h6) .octicon-link {
  color: var(--color-fg-default);
  vertical-align: middle;
  visibility: hidden;
}

:is(h1, h2, h3, h4, h5, h6):hover .octicon-link {
  visibility: visible;
}

Syntax

No syntax is applicable.

Types

This package is fully typed with TypeScript. It exports the additional types Behavior, Build, and Options.

Compatibility

Projects maintained by the unified collective are compatible with all maintained versions of Node.js. As of now, that is Node.js 16+. Our projects sometimes work with older versions, but this is not guaranteed.

This plugin works with rehype-parse version 3+, rehype-stringify version 3+, rehype version 5+, and unified version 6+.

Security

This package is unsafe because of DOM clobbering. It can be made safe with rehype-sanitize. See its readme for more info.

Related

Contribute

See contributing.md in rehypejs/.github for ways to get started. See support.md for ways to get help.

This project has a code of conduct. By interacting with this repository, organization, or community you agree to abide by its terms.

Notice

This project is not affiliated with GitHub.

License

MIT © Titus Wormer