readme.md

mdast-zone

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

Contents

• What is this?
• When should I use this?
• Install
• Use
• API
  • zone(tree, name, handler)
  • Handler
  • Info
• Types
• Compatibility
• Security
• Related
• Contribute
• 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, does the same but uses a heading to mark the start and end of sections.

Install

This package is ESM only. In Node.js (version 16+), install with npm:

npm install mdast-zone

In Deno with esm.sh:

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

In browsers with esm.sh:

<script type="module">
  import {zone} from 'https://esm.sh/mdast-zone@6?bundle'
</script>

Use

Say we have the following file, example.md:

<!--foo start-->

Foo

<!--foo end-->

…and a module example.js:

/**
 * @import {Plugin} from 'unified'
 * @import {Root} from 'mdast'
 */

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 {Plugin<[], 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:

<!--foo start-->

Bar.

<!--foo end-->

API

This package exports the identifier 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) — tree to change
• name (string) — comment name to look for
• handler (Handler) — handle a section

Returns

Nothing (undefined).

Handler

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

Parameters

• start (Node) — start of section
• nodes (Array<Node>) — nodes between start and end
• end (Node) — end of section
• info (Info) — extra info

Returns

Results (Array<Node | null | undefined>, 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) — 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 and 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) 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.

function handler(start, nodes, end) {
  return [start, {type: 'html', value: '<script>alert(1)</script>'}, end]
}

Yields:

<!--foo start-->

<script>alert(1)</script>

<!--foo end-->

Either do not use user input or use hast-util-santize.

Related

• mdast-util-heading-range — similar but uses headings to mark sections

Contribute

See contributing.md in syntax-tree/.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