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mdast extensions to parse and serialize GFM footnotes.

Contents

What is this?

This package contains two extensions that add support for GFM footnote syntax in markdown to mdast. These extensions plug into mdast-util-from-markdown (to support parsing footnotes in markdown into a syntax tree) and mdast-util-to-markdown (to support serializing footnotes in syntax trees to markdown).

GFM footnotes were announced September 30, 2021 but are not specified. Their implementation on github.com is currently buggy. The bugs have been reported on cmark-gfm.

When to use this

You can use these extensions when you are working with mdast-util-from-markdown and mdast-util-to-markdown already.

When working with mdast-util-from-markdown, you must combine this package with micromark-extension-gfm-footnote.

When you don’t need a syntax tree, you can use micromark directly with micromark-extension-gfm-footnote.

When you are working with syntax trees and want all of GFM, use mdast-util-gfm instead.

All these packages are used remark-gfm, which focusses on making it easier to transform content by abstracting these internals away.

This utility does not handle how markdown is turned to HTML. That’s done by mdast-util-to-hast. If your content is not in English, you should configure that utility.

Install

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

npm install mdast-util-gfm-footnote

In Deno with esm.sh:

import {gfmFootnoteFromMarkdown, gfmFootnoteToMarkdown} from 'https://esm.sh/mdast-util-gfm-footnote@2'

In browsers with esm.sh:

<script type="module">
  import {gfmFootnoteFromMarkdown, gfmFootnoteToMarkdown} from 'https://esm.sh/mdast-util-gfm-footnote@2?bundle'
</script>

Use

Say our document example.md contains:

Hi![^1]

[^1]: big note

…and our module example.js looks as follows:

import fs from 'node:fs/promises'
import {fromMarkdown} from 'mdast-util-from-markdown'
import {toMarkdown} from 'mdast-util-to-markdown'
import {gfmFootnote} from 'micromark-extension-gfm-footnote'
import {gfmFootnoteFromMarkdown, gfmFootnoteToMarkdown} from 'mdast-util-gfm-footnote'

const doc = await fs.readFile('example.md')

const tree = fromMarkdown(doc, {
  extensions: [gfmFootnote()],
  mdastExtensions: [gfmFootnoteFromMarkdown()]
})

console.log(tree)

const out = toMarkdown(tree, {extensions: [gfmFootnoteToMarkdown()]})

console.log(out)

…now running node example.js yields (positional info removed for brevity):

{
  type: 'root',
  children: [
    {
      type: 'paragraph',
      children: [
        {type: 'text', value: 'Hi!'},
        {type: 'footnoteReference', identifier: '1', label: '1'}
      ]
    },
    {
      type: 'footnoteDefinition',
      identifier: '1',
      label: '1',
      children: [
        {type: 'paragraph', children: [{type: 'text', value: 'big note'}]}
      ]
    }
  ]
}

Hi\![^1]

[^1]: big note

API

This package exports the identifiers gfmFootnoteFromMarkdown and gfmFootnoteToMarkdown. There is no default export.

gfmFootnoteFromMarkdown()

Create an extension for mdast-util-from-markdown to enable GFM footnotes in markdown.

Returns

Extension for mdast-util-from-markdown (FromMarkdownExtension).

gfmFootnoteToMarkdown()

Create an extension for mdast-util-to-markdown to enable GFM footnotes in markdown.

Returns

Extension for mdast-util-to-markdown (ToMarkdownExtension).

HTML

This utility does not handle how markdown is turned to HTML. That’s done by mdast-util-to-hast. If your content is not in English, you should configure that utility.

Syntax

See Syntax in micromark-extension-gfm-footnote.

Syntax tree

The following interfaces are added to mdast by this utility.

Nodes

FootnoteDefinition

interface FootnoteDefinition <: Parent {
  type: 'footnoteDefinition'
  children: [FlowContent]
}

FootnoteDefinition includes Association

FootnoteDefinition (Parent) represents content relating to the document that is outside its flow.

FootnoteDefinition can be used where flow content is expected. Its content model is also flow content.

FootnoteDefinition includes the mixin Association.

FootnoteDefinition should be associated with FootnoteReferences.

For example, the following markdown:

[^alpha]: bravo and charlie.

Yields:

{
  type: 'footnoteDefinition',
  identifier: 'alpha',
  label: 'alpha',
  children: [{
    type: 'paragraph',
    children: [{type: 'text', value: 'bravo and charlie.'}]
  }]
}

FootnoteReference

interface FootnoteReference <: Node {
  type: 'footnoteReference'
}

FootnoteReference includes Association

FootnoteReference (Node) represents a marker through association.

FootnoteReference can be used where phrasing content is expected. It has no content model.

FootnoteReference includes the mixin Association.

FootnoteReference should be associated with a FootnoteDefinition.

For example, the following markdown:

[^alpha]

Yields:

{
  type: 'footnoteReference',
  identifier: 'alpha',
  label: 'alpha'
}

Content model

FlowContent (GFM footnotes)

type FlowContentGfm = FootnoteDefinition | FlowContent

PhrasingContent (GFM footnotes)

type PhrasingContentGfm = FootnoteReference | PhrasingContent

Types

This package is fully typed with TypeScript. It does not export additional types.

The FootnoteDefinition and FootnoteReference types of the mdast nodes are exposed from @types/mdast.

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-gfm-footnote@^2, compatible with Node.js 16.

Related

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

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