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Add improved docs
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Closes GH-11.

Reviewed-by: Christian Murphy <[email protected]>
Reviewed-by: Remco Haszing <[email protected]>
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@wooorm
wooorm authored Dec 30, 2021
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2 changes: 1 addition & 1 deletion index.js
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Expand Up @@ -13,7 +13,7 @@ const slugs = new Slugger()
/**
* Plugin to add `id`s to headings.
*
* @type {import('unified').Plugin<[], Root>}
* @type {import('unified').Plugin<Array<void>, Root>}
*/
export default function rehypeSlug() {
return (tree) => {
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144 changes: 109 additions & 35 deletions readme.md
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[![Backers][backers-badge]][collective]
[![Chat][chat-badge]][chat]

[**rehype**][rehype] plugin to add `id`s to headings.
**[rehype][]** plugin to add `id`s to headings.

## Contents

* [What is this?](#what-is-this)
* [When should I use this?](#when-should-i-use-this)
* [Install](#install)
* [Use](#use)
* [API](#api)
* [`unified().use(rehypeSlug)`](#unifieduserehypeslug)
* [Types](#types)
* [Compatibility](#compatibility)
* [Security](#security)
* [Related](#related)
* [Contribute](#contribute)
* [License](#license)

## What is this?

This package is a [unified][] ([rehype][]) plugin to add `id`s to headings.
It looks for headings (so `<h1>` through `<h6>`) that do not yet have `id`s
and adds `id` attributes to them based on their textual content.
The algorithm that generates `id`s is [`github-slugger`][github-slugger], which
matches how GitHub works.

**unified** is a project that transforms content with abstract syntax trees
(ASTs).
**rehype** adds support for HTML to unified.
**hast** is the HTML AST that rehype uses.
This is a rehype plugin that adds links to headings in the AST.

## When should I use this?

This plugin is useful when you have relatively long documents and you want to be
able to link to particular sections.

A different plugin, [`rehype-autolink-headings`][rehype-autolink-headings], adds
links to these headings back to themselves, which is useful as it lets users
more easily link to particular sections.

## Install

This package is [ESM only](https://gist.github.com/sindresorhus/a39789f98801d908bbc7ff3ecc99d99c):
Node 12+ is needed to use it and it must be `import`ed instead of `require`d.

[npm][]:
This package is [ESM only](https://gist.github.com/sindresorhus/a39789f98801d908bbc7ff3ecc99d99c).
In Node.js (version 12.20+, 14.14+, or 16.0+), install with [npm][]:

```sh
npm install rehype-slug
```

In Deno with [Skypack][]:

```js
import rehypeSlug from 'https://cdn.skypack.dev/rehype-slug@5?dts'
```

In browsers with [Skypack][]:

```html
<script type="module">
import rehypeSlug from 'https://cdn.skypack.dev/rehype-slug@5?min'
</script>
```

## Use

Say we have the following file, `fragment.html`:
Say we have the following file `example.html`:

```html
<h1>Lorem ipsum 😪</h1>
<h2>dolor—sit—amet</h2>
<h1 id=some-id>Lorem ipsum</h1>
<h2>Dolor sit amet 😪</h2>
<h3>consectetur &amp; adipisicing</h3>
<h4>elit</h4>
<h5>elit</h5>
```

And our script, `example.js`, looks as follows:
And our module `example.js` looks as follows:

```js
import fs from 'node:fs'
import {read} from 'to-vfile'
import {rehype} from 'rehype'
import slug from 'rehype-slug'
import rehypeSlug from 'rehype-slug'

const buf = fs.readFileSync('fragment.html')
main()

rehype()
.data('settings', {fragment: true})
.use(slug)
.process(buf)
.then((file) => {
console.log(String(file))
})
async function main() {
const file = await rehype()
.data('settings', {fragment: true})
.use(rehypeSlug)
.process(await read('example.html'))

console.log(String(file))
}
```

Now, running `node example` yields:
Now, running `node example.js` yields:

```html
<h1 id="lorem-ipsum-">Lorem ipsum 😪</h1>
<h2 id="dolorsitamet">dolor—sit—amet</h2>
<h1 id="some-id">Lorem ipsum</h1>
<h2 id="dolor-sit-amet-">Dolor sit amet 😪</h2>
<h3 id="consectetur--adipisicing">consectetur &#x26; adipisicing</h3>
<h4 id="elit">elit</h4>
<h5 id="elit-1">elit</h5>
Expand All @@ -68,24 +119,37 @@ The default export is `rehypeSlug`.

### `unified().use(rehypeSlug)`

Add `id` properties to h1-h6 headings that don’t already have one.
Add `id`s to headings.
There are no options.

## Types

Uses [**github-slugger**][ghslug] to create GitHub style `id`s.
This package is fully typed with [TypeScript][].
There are no extra exported types.

## Compatibility

Projects maintained by the unified collective are compatible with all maintained
versions of Node.js.
As of now, that is Node.js 12.20+, 14.14+, and 16.0+.
Our projects sometimes work with older versions, but this is not guaranteed.

This plugin works with `rehype-parse` version 1+, `rehype-stringify` version 1+,
`rehype` version 1+, and `unified` version 4+.

## Security

Use of `rehype-slug` can open you up to a [cross-site scripting (XSS)][xss]
attack as it sets `id` attributes on headings.
In a browser, elements are retrievable by `id` with JavaScript and CSS.
If a user injects a heading that slugs to an `id` you are already using,
the user content may impersonate the website.

Always be wary with user input and use [`rehype-sanitize`][sanitize].
attack as it sets `id` attributes on headings, which causes what is known
as “DOM clobbering”.
Please use [`rehype-sanitize`][rehype-sanitize] and see its
[Example: headings (DOM clobbering)][rehype-sanitize-example] for information on
how to properly solve it.

## Related

* [`remark-slug`](https://github.com/wooorm/remark-slug)
— Add slugs to headings in markdown
* [`rehype-autolink-headings`][rehype-autolink-headings]
— add links to headings with IDs back to themselves

## Contribute

Expand Down Expand Up @@ -131,6 +195,8 @@ abide by its terms.

[npm]: https://docs.npmjs.com/cli/install

[skypack]: https://www.skypack.dev

[health]: https://github.com/rehypejs/.github

[contributing]: https://github.com/rehypejs/.github/blob/HEAD/contributing.md
Expand All @@ -143,10 +209,18 @@ abide by its terms.

[author]: https://wooorm.com

[rehype]: https://github.com/rehypejs/rehype
[typescript]: https://www.typescriptlang.org

[ghslug]: https://github.com/Flet/github-slugger
[unified]: https://github.com/unifiedjs/unified

[rehype]: https://github.com/rehypejs/rehype

[xss]: https://en.wikipedia.org/wiki/Cross-site_scripting

[sanitize]: https://github.com/rehypejs/rehype-sanitize
[github-slugger]: https://github.com/Flet/github-slugger

[rehype-autolink-headings]: https://github.com/rehypejs/rehype-autolink-headings

[rehype-sanitize]: https://github.com/rehypejs/rehype-sanitize

[rehype-sanitize-example]: https://github.com/rehypejs/rehype-sanitize#example-headings-dom-clobbering

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