remark-lint-no-multiple-toplevel-headings

remark-lint-no-multiple-toplevel-headings

remark-lint rule to warn when top-level headings are used multiple times.

Contents

• What is this?
• When should I use this?
• Presets
• Install
• Use
• API
  • unified().use(remarkLintNoMultipleToplevelHeadings[, options])
  • Depth
  • Options
• Recommendation
• Examples
• Compatibility
• Contribute
• License

What is this?

This package checks that top-level headings are unique.

When should I use this?

You can use this package to check heading structure.

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-no-multiple-toplevel-headings

In Deno with esm.sh:

import remarkLintNoMultipleToplevelHeadings from 'https://esm.sh/remark-lint-no-multiple-toplevel-headings@4'

In browsers with esm.sh:

<script type="module">
  import remarkLintNoMultipleToplevelHeadings from 'https://esm.sh/remark-lint-no-multiple-toplevel-headings@4?bundle'
</script>

Use

On the API:

import remarkLint from 'remark-lint'
import remarkLintNoMultipleToplevelHeadings from 'remark-lint-no-multiple-toplevel-headings'
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(remarkLintNoMultipleToplevelHeadings)
  .use(remarkStringify)
  .process(file)

console.error(reporter(file))

On the CLI:

remark --frail --use remark-lint --use remark-lint-no-multiple-toplevel-headings .

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

 …
 "remarkConfig": {
   "plugins": [
     …
     "remark-lint",
+    "remark-lint-no-multiple-toplevel-headings",
     …
   ]
 }
 …

API

This package exports no identifiers. It exports the TypeScript types Depth and Options. The default export is remarkLintNoMultipleToplevelHeadings.

unified().use(remarkLintNoMultipleToplevelHeadings[, options])

Warn when top-level headings are used multiple times.

Parameters

• options (Options, default: 1) — configuration

Returns

Transform (Transformer from unified).

Depth

Depth (TypeScript type).

Type

type Depth = 1 | 2 | 3 | 4 | 5 | 6

Options

Configuration (TypeScript type).

Type

type Options = Depth

Recommendation

Documents should almost always have one main heading, which is typically a heading with a rank of 1.

Examples

ok.md

In

# Mercury

## Venus

Out

No messages.

not-ok.md

In

# Venus

# Mercury

Out

3:1-3:10: Unexpected duplicate toplevel heading, exected a single heading with rank `1`

not-ok.md

When configured with 2.

In

## Venus

## Mercury

Out

3:1-3:11: Unexpected duplicate toplevel heading, exected a single heading with rank `2`

html.md

In

Venus <b>and</b> mercury.

<h1>Earth</h1>

<h1>Mars</h1>

Out

5:1-5:14: Unexpected duplicate toplevel heading, exected a single heading with rank `1`

mdx.mdx

In

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

Venus <b>and</b> mercury.

<h1>Earth</h1>
<h1>Mars</h1>

Out

4:1-4:14: Unexpected duplicate toplevel heading, exected a single heading with rank `1`

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-no-multiple-toplevel-headings@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.

License

MIT © Titus Wormer