remark-lint-no-duplicate-headings

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remark-lintgithub-remark-lint rule to warn when the same text is used in multiple headings.

Contents

• What is this?
• When should I use this?
• Presets
• Install
• Use
• API

unified().use(remarkLintNoDuplicateHeadings)

• Recommendation
• Examples
• Compatibility
• Contribute
• License

What is this?

This package checks that headings are unique.

When should I use this?

You can use this package to check that headings are unique.

Presets

This plugin is included in the following presets:
| Preset | Options | | - | - | | remark-preset-lint-markdown-style-guide | |

Install

This package is ESM onlygithub-gist-esm. In Node.js (version 16+), install with npmnpm-install:

npm install remark-lint-no-duplicate-headings

In Deno with esm.shesm-sh:

import remarkLintNoDuplicateHeadings from 'https://esm.sh/remark-lint-no-duplicate-headings@4'

In browsers with esm.shesm-sh:

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

Use

On the API:

import remarkLint from 'remark-lint'
import remarkLintNoDuplicateHeadings from 'remark-lint-no-duplicate-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(remarkLintNoDuplicateHeadings)
  .use(remarkStringify)
  .process(file)

console.error(reporter(file))

On the CLI:

remark --frail --use remark-lint --use remark-lint-no-duplicate-headings .

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

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

API

This package exports no identifiers. It exports no additional TypeScripttypescript types. The default export is remarkLintNoDuplicateHeadingsapi-remark-lint-no-duplicate-headings.

unified().use(remarkLintNoDuplicateHeadings)

Warn when the same text is used in multiple headings.

Parameters

There are no options.

Returns

Transform (Transformer from unifiedgithub-unified-transformer).

Recommendation

Headings having unique text helps screen reader users, who typically use “jump to heading” features to navigate within a page, which reads headings out loud.
It also helps because often headings receive automatic unique IDs, and when the same heading text is used, they are suffixed with a number based on where they are positioned in the document, which makes linking to them prone to changes.

Examples

ok.md

In

# Mercury

## Venus

Out

No messages.

not-ok.md

In

# Mercury

## Mercury

## [Mercury](http://example.com/mercury/)

Out

3:1-3:11: Unexpected heading with equivalent text, expected unique headings
5:1-5:42: Unexpected heading with equivalent text, expected unique headings

mdx.mdx

In

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

<h1>Mercury</h1>
<h2>Mercury</h2>

Out

2:1-2:17: Unexpected heading with equivalent text, expected unique headings

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-duplicate-headings@4, compatible with Node.js 16.

Contribute

See contributing.mdgithub-dotfiles-contributing in remarkjs/.githubgithub-dotfiles-health for ways to get started. See support.mdgithub-dotfiles-support for ways to get help.
This project has a code of conductgithub-dotfiles-coc. By interacting with this repository, organization, or community you agree to abide by its terms.

License

MITfile-license © Titus Wormerauthor