mdast-util-heading-range

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

Contents

• What is this?
• When should I use this?
• Install
• Use
• API
  • headingRange(tree, test|options, handler)
  • Handler
  • Info
  • Options
  • Test
  • TestFunction
• 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 16+), install with npm:

npm install mdast-util-heading-range

In Deno with esm.sh:

import {headingRange} from 'https://esm.sh/mdast-util-heading-range@4'

In browsers with esm.sh:

<script type="module">
  import {headingRange} from 'https://esm.sh/mdast-util-heading-range@4?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 function (tree) {
    headingRange(tree, 'foo', function (start, nodes, end) {
      return [
        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 (undefined).

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

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 or undefined) — index of end in parent

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 = RegExp | TestFunction | string

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 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-util-heading-range@^4, 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.

/** @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.

Related

• 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.

License

MIT © Titus Wormer