mdast-util-heading-range

mdast utility to find headings and replace the content in their section.

What is this?
When should I use this?
Install
Use
API
Types
Compatibility
Security
Related
Contribute
License

What is this?

This package is a utility that lets you find a certain heading, then takes the content in their section (from it to the next heading of the same or lower depth), 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. For example, this utility is used by remark-toc to update the above Contents heading.

A similar package, mdast-zone, does the same but uses comments to mark the start and end of sections.

Install

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

npm install mdast-util-heading-range

In Deno with esm.sh:

import {headingRange} from 'https://esm.sh/mdast-util-heading-range@3'

In browsers with esm.sh:

<script type="module">
  import {headingRange} from 'https://esm.sh/mdast-util-heading-range@3?bundle'
</script>

Use

Say we have the following file, example.md:

# Foo

Bar.

# Baz

…and a module example.js:

import {read} from 'to-vfile'
import {remark} from 'remark'
import {headingRange} from 'mdast-util-heading-range'

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 (tree) => {
    headingRange(tree, 'foo', (start, nodes, end) => [
      start,
      {type: 'paragraph', children: [{type: 'text', value: 'Qux.'}]},
      end
    ])
  }
}

…now running node example.js yields:

# Foo

Qux.

# Baz

API

This package exports the identifier headingRange. There is no default export.

`headingRange(tree, test|options, handler)`

Search tree for a heading matching test and change its “section” with handler.

A “section” ranges from the matched heading until the next heading of the same or lower depth, or the end of the document.

If ignoreFinalDefinitions: true, final definitions “in” the section are excluded.

Parameters

tree (Node) — tree to change
test (Test) — same as passing {test: Test}
options (Options) — configuration
handler (Handler) — handle a section

Returns

Nothing (void).

`Handler`

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

Parameters

start (Heading) — start of section (a heading node matching test)
nodes (Array<Node>) — nodes between start and end
end (Node or undefined) — end of section, if any
info (Info) — extra info

`Info`

Extra info (TypeScript type).

Fields

parent (Node) — parent of the section
start (number) — index of start in parent
end (number or null) — index of end in parent

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.

`Options`

Configuration (TypeScript type).

Fields

test (Test) — test for a heading
ignoreFinalDefinitions (boolean, default: false) — ignore final definitions otherwise in the section

`Test`

Test for a heading (TypeScript type).

When string, wrapped in new RegExp('^(' + value + ')$', 'i'); when RegExp, wrapped in (value) => expression.test(value)

Type

export type Test = string | RegExp | TestFunction

`TestFunction`

Check if a node matches (TypeScript type).

Parameters

value (string) — plain-text heading
node (Heading) — heading node

Returns

Whether this is the heading that is searched for (boolean, optional).

Types

This package is fully typed with TypeScript. This package exports the types Handler, Info, Options, Test, and TestFunction.

Compatibility

Projects maintained by the unified collective are compatible with all maintained versions of Node.js. As of now, that is Node.js 14.14+ and 16.0+. Our projects sometimes work with older versions, but this is not guaranteed.

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.

/** @type {import('mdast-util-heading-range').Handler} */
function handler(start, nodes, end) {
  return [start, {type: 'html', value: '<script>alert(1)</script>'}, end]
}

Yields:

# Foo

<script>alert(1)</script>

# Baz

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

mdast-zone — similar but uses comments to mark the start and end of 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, organisation, or community you agree to abide by its terms.