remark-lint-heading-increment

remark-lint rule to warn when heading ranks increment with more than 1 at a time.

What is this?

This package checks the increase of headings.

When should I use this?

You can use this package to check the increase of headings.

Presets

This plugin is included in the following presets:

Preset	Options
`remark-preset-lint-markdown-style-guide`

Install

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

npm install remark-lint-heading-increment

In Deno with esm.sh:

import remarkLintHeadingIncrement from 'https://esm.sh/remark-lint-heading-increment@4'

In browsers with esm.sh:

<script type="module">
  import remarkLintHeadingIncrement from 'https://esm.sh/remark-lint-heading-increment@4?bundle'
</script>

Use

On the API:

import remarkLint from 'remark-lint'
import remarkLintHeadingIncrement from 'remark-lint-heading-increment'
import remarkParse from 'remark-parse'
import remarkStringify from 'remark-stringify'
import {read} from 'to-vfile'
import {unified} from 'unified'
import {reporter} from 'vfile-reporter'

const file = await read('example.md')

await unified()
  .use(remarkParse)
  .use(remarkLint)
  .use(remarkLintHeadingIncrement)
  .use(remarkStringify)
  .process(file)

console.error(reporter(file))

On the CLI:

remark --frail --use remark-lint --use remark-lint-heading-increment .

On the CLI in a config file (here a package.json):

 …
 "remarkConfig": {
   "plugins": [
     …
     "remark-lint",
+    "remark-lint-heading-increment",
     …
   ]
 }
 …

API

This package exports no identifiers. It exports no additional TypeScript types. The default export is remarkLintHeadingIncrement.

`unified().use(remarkLintHeadingIncrement)`

Warn when heading ranks increment with more than 1 at a time.

Parameters

There are no options.

Returns

Transform (Transformer from unified).

Recommendation

While markdown is not only used for HTML, HTML accessibility guidelines state that headings should increment by one at a time. As in, say the previous heading had a rank of 2 (so <h2>), then the following heading that is to be considered “inside” it should have a rank of 3 (<h3>). Due to this, when HTML output is a goal of the document, it’s recommended that this rule is turned on.

Examples

`ok.md`

In

# Mercury

## Nomenclature

Out

No messages.

`also-ok.md`

In

#### Impact basins and craters

#### Plains

#### Compressional features

Out

No messages.

`not-ok.md`

In

# Mercury

### Internal structure

### Surface geology

## Observation history

#### Mariner 10

Out

3:1-3:23: Unexpected heading rank `3`, exected rank `2`
5:1-5:20: Unexpected heading rank `3`, exected rank `2`
9:1-9:16: Unexpected heading rank `4`, exected rank `3`

`html.md`

In

# Mercury

<b>Mercury</b> is the first planet from the Sun and the smallest
in the Solar System.

<h3>Internal structure</h3>

<h2>Orbit, rotation, and longitude</h2>

Out

6:1-6:28: Unexpected heading rank `3`, exected rank `2`

`mdx.mdx`

In

👉 Note: this example uses MDX (remark-mdx).

# Mercury

<b>Mercury</b> is the first planet from the Sun and the smallest
in the Solar System.

<h3>Internal structure</h3>

<h2>Orbit, rotation, and longitude</h2>

Out

6:1-6:28: Unexpected heading rank `3`, exected rank `2`

Compatibility

Projects maintained by the unified collective are compatible with maintained versions of Node.js.

When we cut a new major release, we drop support for unmaintained versions of Node. This means we try to keep the current release line, remark-lint-heading-increment@4, compatible with Node.js 16.

Contribute

See contributing.md in remarkjs/.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.

unified

Project: remarkjs/remark-lint

Package: remark-lint-heading-increment@3.1.1