mdast-util-gfm

What is mdast-util-gfm?

The `mdast-util-gfm` package is a utility for working with GitHub Flavored Markdown (GFM) in the MDAST (Markdown Abstract Syntax Tree) format. It provides functions to parse and transform GFM-specific syntax such as tables, strikethroughs, task lists, and autolinks.

What are mdast-util-gfm's main functionalities?

Tables

This feature allows you to parse and transform GitHub Flavored Markdown tables into an MDAST tree structure.

const { fromMarkdown, toMarkdown } = require('mdast-util-gfm');
const markdown = '| Header1 | Header2 |
| ------- | ------- |
| Cell1   | Cell2   |';
const tree = fromMarkdown(markdown);
console.log(tree);

Strikethrough

This feature allows you to parse and transform strikethrough text in GitHub Flavored Markdown into an MDAST tree structure.

const { fromMarkdown, toMarkdown } = require('mdast-util-gfm');
const markdown = 'This is ~~strikethrough~~ text.';
const tree = fromMarkdown(markdown);
console.log(tree);

Task Lists

This feature allows you to parse and transform task lists in GitHub Flavored Markdown into an MDAST tree structure.

const { fromMarkdown, toMarkdown } = require('mdast-util-gfm');
const markdown = '- [x] Task 1
- [ ] Task 2';
const tree = fromMarkdown(markdown);
console.log(tree);

Autolinks

This feature allows you to parse and transform autolinks in GitHub Flavored Markdown into an MDAST tree structure.

const { fromMarkdown, toMarkdown } = require('mdast-util-gfm');
const markdown = 'Visit https://example.com for more info.';
const tree = fromMarkdown(markdown);
console.log(tree);

Other packages similar to mdast-util-gfm

remark-gfm

The `remark-gfm` package is a plugin for the `remark` ecosystem that adds support for GitHub Flavored Markdown. It provides similar functionality to `mdast-util-gfm` but is designed to be used within the `remark` processor.

markdown-it

The `markdown-it` package is a Markdown parser that supports GitHub Flavored Markdown out of the box. It is a more general-purpose parser compared to `mdast-util-gfm`, which is specifically designed for working with MDAST.

marked

The `marked` package is a fast Markdown parser and compiler that supports GitHub Flavored Markdown. It is similar to `markdown-it` in that it is a general-purpose parser, but it is known for its speed and performance.

README

mdast-util-gfm

mdast extensions to parse and serialize GFM (autolink literals, footnotes, strikethrough, tables, tasklists).

Contents

• What is this?
• When to use this
• Install
• Use
• API
  • gfmFromMarkdown()
  • gfmToMarkdown(options?)
  • Options
• HTML
• Syntax
• Syntax tree
• Types
• Compatibility
• Related
• Contribute
• License

What is this?

This package contains two extensions that add support for GFM syntax in markdown to mdast: autolink literals (www.x.com), footnotes ([^1]), strikethrough (~~stuff~~), tables (| cell |…), and tasklists (* [x]). These extensions plug into mdast-util-from-markdown (to support parsing GFM in markdown into a syntax tree) and mdast-util-to-markdown (to support serializing GFM in syntax trees to markdown).

When to use this

This project is useful when you want to support the same features that GitHub does in files in a repo, Gists, and several other places. Users frequently believe that some of these extensions, specifically autolink literals and tables, are part of normal markdown, so using mdast-util-gfm will help match your implementation to their understanding of markdown. There are several edge cases where GitHub’s implementation works in unexpected ways or even different than described in their spec, so writing in GFM is not always the best choice.

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.

Instead of this package, you can also use the extensions separately:

• mdast-util-gfm-autolink-literal — support GFM autolink literals
• mdast-util-gfm-footnote — support GFM footnotes
• mdast-util-gfm-strikethrough — support GFM strikethrough
• mdast-util-gfm-table — support GFM tables
• mdast-util-gfm-task-list-item — support GFM tasklists

A different utility, mdast-util-frontmatter, adds support for frontmatter. GitHub supports YAML frontmatter for files in repos and Gists but they don’t treat it as part of GFM.

All these packages are used in 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

In Deno with esm.sh:

import {gfmFromMarkdown, gfmToMarkdown} from 'https://esm.sh/mdast-util-gfm@3'

In browsers with esm.sh:

<script type="module">
  import {gfmFromMarkdown, gfmToMarkdown} from 'https://esm.sh/mdast-util-gfm@3?bundle'
</script>

Use

Say our document example.md contains:

# GFM

## Autolink literals

www.example.com, https://example.com, and [e-mail].

## Footnote

A note[^1]

[^1]: Big note.

## Strikethrough

~one~ or ~~two~~ tildes.

## Table

| a | b  |  c |  d  |
| - | :- | -: | :-: |

## Tasklist

* [ ] to do
* [x] done

…and our module example.js looks as follows:

import fs from 'node:fs/promises'
import {fromMarkdown} from 'mdast-util-from-markdown'
import {gfmFromMarkdown, gfmToMarkdown} from 'mdast-util-gfm'
import {toMarkdown} from 'mdast-util-to-markdown'
import {gfm} from 'micromark-extension-gfm'

const value = await fs.readFile('example.md', 'utf8')

const tree = fromMarkdown(value, {
  extensions: [gfm()],
  mdastExtensions: [gfmFromMarkdown()]
})

console.log(tree)

const result = toMarkdown(tree, {extensions: [gfmToMarkdown()]})

console.log(result)

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

{
  type: 'root',
  children: [
    {type: 'heading', depth: 1, children: [{type: 'text', value: 'GFM'}]},
    {
      type: 'heading',
      depth: 2,
      children: [{type: 'text', value: 'Autolink literals'}]
    },
    {
      type: 'paragraph',
      children: [
        {
          type: 'link',
          title: null,
          url: 'http://www.example.com',
          children: [{type: 'text', value: 'www.example.com'}]
        },
        {type: 'text', value: ', '},
        {
          type: 'link',
          title: null,
          url: 'https://example.com',
          children: [{type: 'text', value: 'https://example.com'}]
        },
        {type: 'text', value: ', and '},
        {
          type: 'link',
          title: null,
          url: 'mailto:[e-mail]',
          children: [{type: 'text', value: '[e-mail]'}]
        },
        {type: 'text', value: '.'}
      ]
    },
    {type: 'heading', depth: 2, children: [{type: 'text', value: 'Footnote'}]},
    {
      type: 'paragraph',
      children: [
        {type: 'text', value: 'A note'},
        {type: 'footnoteReference', identifier: '1', label: '1'}
      ]
    },
    {
      type: 'footnoteDefinition',
      identifier: '1',
      label: '1',
      children: [
        {type: 'paragraph', children: [{type: 'text', value: 'Big note.'}]}
      ]
    },
    {
      type: 'heading',
      depth: 2,
      children: [{type: 'text', value: 'Strikethrough'}]
    },
    {
      type: 'paragraph',
      children: [
        {
          type: 'delete',
          children: [{type: 'text', value: 'one'}]
        },
        {type: 'text', value: ' or '},
        {
          type: 'delete',
          children: [{type: 'text', value: 'two'}]
        },
        {type: 'text', value: ' tildes.'}
      ]
    },
    {type: 'heading', depth: 2, children: [{type: 'text', value: 'Table'}]},
    {
      type: 'table',
      align: [null, 'left', 'right', 'center'],
      children: [
        {
          type: 'tableRow',
          children: [
            {type: 'tableCell', children: [{type: 'text', value: 'a'}]},
            {type: 'tableCell', children: [{type: 'text', value: 'b'}]},
            {type: 'tableCell', children: [{type: 'text', value: 'c'}]},
            {type: 'tableCell', children: [{type: 'text', value: 'd'}]}
          ]
        }
      ]
    },
    {type: 'heading', depth: 2, children: [{type: 'text', value: 'Tasklist'}]},
    {
      type: 'list',
      ordered: false,
      start: null,
      spread: false,
      children: [
        {
          type: 'listItem',
          spread: false,
          checked: false,
          children: [
            {type: 'paragraph', children: [{type: 'text', value: 'to do'}]}
          ]
        },
        {
          type: 'listItem',
          spread: false,
          checked: true,
          children: [
            {type: 'paragraph', children: [{type: 'text', value: 'done'}]}
          ]
        }
      ]
    }
  ]
}

# GFM

## Autolink literals

[www.example.com](http://www.example.com), <https://example.com>, and <[e-mail]>.

## Footnote

A note[^1]

[^1]: Big note.

## Strikethrough

~~one~~ or ~~two~~ tildes.

## Table

| a | b  |  c |  d  |
| - | :- | -: | :-: |

## Tasklist

*   [ ] to do
*   [x] done

API

This package exports the identifiers gfmFromMarkdown and gfmToMarkdown. There is no default export.

gfmFromMarkdown()

Create an extension for mdast-util-from-markdown to enable GFM (autolink literals, footnotes, strikethrough, tables, tasklists).

Returns

Extension for mdast-util-from-markdown to enable GFM (Array<FromMarkdownExtension>).

gfmToMarkdown(options?)

Create an extension for mdast-util-to-markdown to enable GFM (autolink literals, footnotes, strikethrough, tables, tasklists).

Parameters

• options (Options) — configuration

Returns

Extension for mdast-util-to-markdown to enable GFM (Array<ToMarkdownExtension>).

Options

Configuration (TypeScript type).

Fields

• firstLineBlank (boolean, default: false) — use a blank line for the first line of footnote definitions
• stringLength (((value: string) => number), default: s => s.length) — function to detect the length of table cell content, used when aligning the delimiters between cells
• tableCellPadding (boolean, default: true) — whether to add a space of padding between delimiters and cells
• tablePipeAlign (boolean, default: true) — whether to align the delimiters

HTML

This utility does not handle how markdown is turned to HTML. That’s done by mdast-util-to-hast.

Syntax

See Syntax in micromark-extension-gfm.

Syntax tree

This utility combines several mdast utilities. See their readmes for the node types supported in the tree:

• mdast-util-gfm-autolink-literal — GFM autolink literals
• mdast-util-gfm-footnote — GFM footnotes
• mdast-util-gfm-strikethrough — GFM strikethrough
• mdast-util-gfm-table — GFM tables
• mdast-util-gfm-task-list-item — GFM tasklists

Types

This package is fully typed with TypeScript. It exports the additional type Options.

The Delete, FootnoteDefinition, FootnoteReference, Table, TableRow, and TableCell 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@^3, compatible with Node.js 16.

Related

• remark-gfm — remark plugin to support GFM
• micromark-extension-gfm — micromark extension to parse GFM

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