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https://github.com/syntax-tree/mdast-zone

utility to treat HTML comments as ranges or markers in mdast
https://github.com/syntax-tree/mdast-zone

mdast mdast-util syntax-tree unist util zone

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utility to treat HTML comments as ranges or markers in mdast

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# mdast-zone



[![Build][build-badge]][build]

[![Coverage][coverage-badge]][coverage]

[![Downloads][downloads-badge]][downloads]

[![Size][size-badge]][size]

[![Sponsors][sponsors-badge]][collective]

[![Backers][backers-badge]][collective]

[![Chat][chat-badge]][chat]



[mdast][] utility to find two comments and replace the content in them.



## Contents



* [What is this?](#what-is-this)

* [When should I use this?](#when-should-i-use-this)

* [Install](#install)

* [Use](#use)

* [API](#api)

  * [`zone(tree, name, handler)`](#zonetree-name-handler)

  * [`Handler`](#handler)

  * [`Info`](#info)

* [Types](#types)

* [Compatibility](#compatibility)

* [Security](#security)

* [Related](#related)

* [Contribute](#contribute)

* [License](#license)



## What is this?



This package is a utility that lets you find certain comments, then takes the

content between them, and calls a given handler with the result, so that you can

change or replace things.



## When should I use this?



This utility is typically useful when you have certain sections that can be

generated.

Comments are a hidden part of markdown, so they can be used as processing

instructions.

You can use those comments to define what content to change or replace.



A similar package, [`mdast-util-heading-range`][mdast-util-heading-range], does

the same but uses a heading to mark the start and end of sections.



## Install



This package is [ESM only][esm].

In Node.js (version 16+), install with [npm][]:



```sh

npm install mdast-zone

```



In Deno with [`esm.sh`][esmsh]:



```js

import {zone} from 'https://esm.sh/mdast-zone@6'

```



In browsers with [`esm.sh`][esmsh]:



```html



  import {zone} from 'https://esm.sh/mdast-zone@6?bundle'



```



## Use



Say we have the following file, `example.md`:



```markdown



Foo



```



…and a module `example.js`:



```js

import {zone} from 'mdast-zone'

import {remark} from 'remark'

import {read} from 'to-vfile'



const file = await remark()

  .use(myPluginThatReplacesFoo)

  .process(await read('example.md'))



console.log(String(file))



/** @type {import('unified').Plugin<[], import('mdast').Root>} */

function myPluginThatReplacesFoo() {

  return function (tree) {

    zone(tree, 'foo', function (start, nodes, end) {

      return [

        start,

        {type: 'paragraph', children: [{type: 'text', value: 'Bar.'}]},

        end

      ]

    })

  }

}

```



…now running `node example.js` yields:



```markdown



Bar.



```



## API



This package exports the identifier [`zone`][api-zone].

There is no default export.



### `zone(tree, name, handler)`



Search `tree` for a start and end comments matching `name` and change their

“section” with `handler`.



###### Parameters



* `tree` ([`Node`][node])

  — tree to change

* `name` (`string`)

  — comment name to look for

* `handler` ([`Handler`][api-handler])

  — handle a section



###### Returns



Nothing (`undefined`).



### `Handler`



Callback called when a section is found (TypeScript type).



###### Parameters



* `start` ([`Node`][node])

  — start of section

* `nodes` ([`Array`][node])

  — nodes between `start` and `end`

* `end` ([`Node`][node])

  — end of section

* `info` ([`Info`][api-info])

  — extra info



###### Returns



Results (`Array`, optional).



If nothing is returned, nothing will be changed.

If an array of nodes (can include `null` and `undefined`) is returned, the

original section will be replaced by those nodes.



### `Info`



Extra info (TypeScript type).



###### Fields



* `parent` ([`Node`][node])

  — parent of the section

* `start` (`number`)

  — index of `start` in `parent`

* `end` (`number`)

  — index of `end` in `parent`



## Types



This package is fully typed with [TypeScript][].

It exports the additional types [`Handler`][api-handler] and

[`Info`][api-info].



## 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-zone@^6`,

compatible with Node.js 16.



## Security



Improper use of `handler` can open you up to a [cross-site scripting (XSS)][xss]

attack as the value it returns is injected into the syntax tree.

This can become a problem if the tree is later transformed to **[hast][]**.

The following example shows how a script is injected that could run when loaded

in a browser.



```js

function handler(start, nodes, end) {

  return [start, {type: 'html', value: 'alert(1)'}, end]

}

```



Yields:



```markdown



alert(1)



```



Either do not use user input or use [`hast-util-santize`][hast-util-sanitize].



## Related



* [`mdast-util-heading-range`](https://github.com/syntax-tree/mdast-util-heading-range)

  — similar but uses headings to mark sections



## 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-zone/workflows/main/badge.svg



[build]: https://github.com/syntax-tree/mdast-zone/actions



[coverage-badge]: https://img.shields.io/codecov/c/github/syntax-tree/mdast-zone.svg



[coverage]: https://codecov.io/github/syntax-tree/mdast-zone



[downloads-badge]: https://img.shields.io/npm/dm/mdast-zone.svg



[downloads]: https://www.npmjs.com/package/mdast-zone



[size-badge]: https://img.shields.io/badge/dynamic/json?label=minzipped%20size&query=$.size.compressedSize&url=https://deno.bundlejs.com/?q=mdast-zone



[size]: https://bundlejs.com/?q=mdast-zone



[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



[xss]: https://en.wikipedia.org/wiki/Cross-site_scripting



[mdast]: https://github.com/syntax-tree/mdast



[node]: https://github.com/syntax-tree/mdast#nodes



[mdast-util-heading-range]: https://github.com/syntax-tree/mdast-util-heading-range



[hast]: https://github.com/syntax-tree/hast



[hast-util-sanitize]: https://github.com/syntax-tree/hast-util-sanitize



[api-zone]: #zonetree-name-handler



[api-handler]: #handler



[api-info]: #info