# mdast-comment-marker
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[mdast][] utility to parse comment markers.
## Contents
* [What is this?](#what-is-this)
* [When should I use this?](#when-should-i-use-this)
* [Install](#install)
* [Use](#use)
* [API](#api)
* [`commentMarker(value)`](#commentmarkervalue)
* [`Marker`](#marker)
* [`MarkerParameters`](#markerparameters)
* [`MarkerParameterValue`](#markerparametervalue)
* [Types](#types)
* [Compatibility](#compatibility)
* [Security](#security)
* [Related](#related)
* [Contribute](#contribute)
* [License](#license)
## What is this?
This package is a utility that tries to parse a structured marker from a
comment.
## When should I use this?
Comments are a hidden part of markdown, so they can be used as processing
instructions.
For example, this utility is used in [`remark-lint`][remark-lint] to control
whether lint rules are turned on or ignored, and by [`mdast-zone`][mdast-zone]
to replace sections between two markers.
## Install
This package is [ESM only][esm].
In Node.js (version 16+), install with [npm][]:
```sh
npm install mdast-comment-marker
```
In Deno with [`esm.sh`][esmsh]:
```js
import {commentMarker} from 'https://esm.sh/mdast-comment-marker@3'
```
In browsers with [`esm.sh`][esmsh]:
```html
```
## Use
```js
import {commentMarker} from 'mdast-comment-marker'
console.log(commentMarker({type: 'html', value: ''}));
console.log(commentMarker({
type: 'html',
value: ''
}));
console.log(commentMarker({type: 'html', value: ''}));
// Also supports MDX expressions:
console.log(commentMarker({
type: 'mdxFlowExpression',
value: '/* lint disable heading-style */'
}));
```
Yields:
```js
{
name: 'foo',
attributes: '',
parameters: {},
node: { type: 'html', value: '' }
}
{
name: 'foo',
attributes: `bar baz=12.4 qux="test test" quux='false'`,
parameters: { bar: true, baz: 12.4, qux: 'test test', quux: false },
node: {
type: 'html',
value: ``
}
}
undefined
{
name: 'lint',
attributes: 'disable heading-style',
parameters: { disable: true, 'heading-style': true },
node: {
type: 'mdxFlowExpression',
value: '/* lint disable heading-style */'
}
}
```
## API
This package exports the identifier [`commentMarker`][api-comment-marker].
There is no default export.
### `commentMarker(value)`
Parse a comment marker.
###### Parameters
* `value` (`unknown`)
— thing to parse, typically [`Node`][node]
###### Returns
Info ([`Marker`][api-marker]) when applicable or `undefined`.
### `Marker`
Comment marker (TypeScript type).
###### Properties
* `name` (`string`)
— name of marker
* `attributes` (`string`)
— value after name
* `parameters` ([`MarkerParameters`][api-marker-parameters])
— parsed attributes
* `node` ([`Node`][node])
— reference to given node
### `MarkerParameters`
Parameters (TypeScript type).
###### type
```ts
type MarkerParameters = Record
```
### `MarkerParameterValue`
Value (TypeScript type).
If it looks like a number (to JavaScript), it’s cast as number.
The strings `true` and `false` are turned into their corresponding
booleans.
The empty string is also considered the `true` boolean.
###### type
```ts
type MarkerParameterValue = number | string | boolean
```
## Types
This package is fully typed with [TypeScript][].
This package exports the types [`Marker`][api-marker],
[`MarkerParameters`][api-marker-parameters], and
[`MarkerParameterValue`][api-marker-parameter-value]
## 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, `mdast-comment-marker@^3`,
compatible with Node.js 16.
## Security
Use of `mdast-comment-marker` does not involve [hast][], user content, or change
the tree, so there are no openings for [cross-site scripting (XSS)][xss]
attacks.
## Related
* [`mdast-zone`](https://github.com/syntax-tree/mdast-zone)
— change or replace a section marked by comments
## Contribute
See [`contributing.md`][contributing] in [`syntax-tree/.github`][health] for
ways to get started.
See [`support.md`][support] for ways to get help.
This project has a [code of conduct][coc].
By interacting with this repository, organization, or community you agree to
abide by its terms.
## License
[MIT][license] © [Titus Wormer][author]
[build-badge]: https://github.com/syntax-tree/mdast-comment-marker/workflows/main/badge.svg
[build]: https://github.com/syntax-tree/mdast-comment-marker/actions
[coverage-badge]: https://img.shields.io/codecov/c/github/syntax-tree/mdast-comment-marker.svg
[coverage]: https://codecov.io/github/syntax-tree/mdast-comment-marker
[downloads-badge]: https://img.shields.io/npm/dm/mdast-comment-marker.svg
[downloads]: https://www.npmjs.com/package/mdast-comment-marker
[size-badge]: https://img.shields.io/badge/dynamic/json?label=minzipped%20size&query=$.size.compressedSize&url=https://deno.bundlejs.com/?q=mdast-comment-marker
[size]: https://bundlejs.com/?q=mdast-comment-marker
[sponsors-badge]: https://opencollective.com/unified/sponsors/badge.svg
[backers-badge]: https://opencollective.com/unified/backers/badge.svg
[collective]: https://opencollective.com/unified
[chat-badge]: https://img.shields.io/badge/chat-discussions-success.svg
[chat]: https://github.com/syntax-tree/unist/discussions
[npm]: https://docs.npmjs.com/cli/install
[esm]: https://gist.github.com/sindresorhus/a39789f98801d908bbc7ff3ecc99d99c
[esmsh]: https://esm.sh
[typescript]: https://www.typescriptlang.org
[license]: license
[author]: https://wooorm.com
[health]: https://github.com/syntax-tree/.github
[contributing]: https://github.com/syntax-tree/.github/blob/main/contributing.md
[support]: https://github.com/syntax-tree/.github/blob/main/support.md
[coc]: https://github.com/syntax-tree/.github/blob/main/code-of-conduct.md
[mdast]: https://github.com/syntax-tree/mdast
[node]: https://github.com/syntax-tree/unist#node
[xss]: https://en.wikipedia.org/wiki/Cross-site_scripting
[hast]: https://github.com/syntax-tree/hast
[remark-lint]: https://github.com/remarkjs/remark-lint
[mdast-zone]: https://github.com/syntax-tree/mdast-zone
[api-comment-marker]: #commentmarkervalue
[api-marker]: #marker
[api-marker-parameters]: #markerparameters
[api-marker-parameter-value]: #markerparametervalue