mdast-util-gfm
mdast extensions to parse and serialize GFM (autolink literals, footnotes, strikethrough, tables, tasklists).
Contents
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:
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 contact@example.com.
## 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 {gfm} from 'micromark-extension-gfm'
import {fromMarkdown} from 'mdast-util-from-markdown'
import {gfmFromMarkdown, gfmToMarkdown} from 'mdast-util-gfm'
import {toMarkdown} from 'mdast-util-to-markdown'
const doc = await fs.readFile('example.md')
const tree = fromMarkdown(doc, {
extensions: [gfm()],
mdastExtensions: [gfmFromMarkdown()]
})
console.log(tree)
const out = toMarkdown(tree, {extensions: [gfmToMarkdown()]})
console.log(out)
…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:contact@example.com',
children: [{type: 'text', value: 'contact@example.com'}]
},
{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 <contact@example.com>.
## 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
Returns
Extension for mdast-util-to-markdown to enable GFM (Array<ToMarkdownExtension>).
Options
Configuration (TypeScript type).
Fields
tableCellPadding (boolean, default: true) — whether to add a space of padding between delimiters and cellstablePipeAlign (boolean, default: true) — whether to align the delimitersstringLength (((value: string) => number), default: s => s.length) — function to detect the length of table cell content, used when aligning the delimiters between cells
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:
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.
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