unified

Project: remarkjs/remark-lint

Package: remark-lint-no-duplicate-headings@3.1.1

  1. Dependents: 11
  2. remark-lint rule to warn on duplicate headings
  1. remark 203
  2. lint 77
  3. rule 72
  4. remark-lint-rule 65
  5. heading 27
  6. duplicate 4

remark-lint-no-duplicate-headings

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remark-lint rule to warn when headings with the same text are found.

Contents

What is this?

This package is a unified (remark) plugin, specifically a remark-lint rule. Lint rules check markdown code style.

When should I use this?

You can use this package to check that headings with the same text are used once.

Presets

This rule is included in the following presets:

PresetSetting
remark-preset-lint-markdown-style-guide

Install

This package is ESM only. In Node.js (version 12.20+, 14.14+, or 16.0+), install with npm:

npm install remark-lint-no-duplicate-headings

In Deno with esm.sh:

import remarkLintNoDuplicateHeadings from 'https://esm.sh/remark-lint-no-duplicate-headings@3'

In browsers with esm.sh:

<script type="module">
  import remarkLintNoDuplicateHeadings from 'https://esm.sh/remark-lint-no-duplicate-headings@3?bundle'
</script>

Use

On the API:

import {read} from 'to-vfile'
import {reporter} from 'vfile-reporter'
import {remark} from 'remark'
import remarkLint from 'remark-lint'
import remarkLintNoDuplicateHeadings from 'remark-lint-no-duplicate-headings'

main()

async function main() {
  const file = await remark()
    .use(remarkLint)
    .use(remarkLintNoDuplicateHeadings)
    .process(await read('example.md'))

  console.error(reporter(file))
}

On the CLI:

remark --use remark-lint --use remark-lint-no-duplicate-headings example.md

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. The default export is remarkLintNoDuplicateHeadings.

unified().use(remarkLintNoDuplicateHeadings[, config])

This rule supports standard configuration that all remark lint rules accept (such as false to turn it off or [1, options] to configure it).

There are no options.

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
# Foo

## Bar
Out

No messages.

not-ok.md
In
# Foo

## Foo

## [Foo](http://foo.com/bar)
Out
3:1-3:7: Do not use headings with similar content (1:1)
5:1-5:29: Do not use headings with similar content (3:1)

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.

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