mdast utility that turns a syntax tree into markdown.

• What is this?
• When should I use this?
• Install
• Use
• API
  • toMarkdown(tree[, options])
• List of extensions
• Syntax
• Syntax tree
• Types
• Security
• Related
• Contribute
• License

This package is a utility that takes an mdast syntax tree as input and turns it into serialized markdown.

This utility is a low level project. It’s used in remark-stringify, which focusses on making it easier to transform content by abstracting these internals away.

If you want to handle syntax trees manually, use this. For an easier time processing content, use the remark ecosystem instead.

You can combine this utility with other utilities to add syntax extensions. Notable examples that deeply integrate with it are mdast-util-gfm, mdast-util-mdx, mdast-util-frontmatter, mdast-util-math, and mdast-util-directive.

This package is ESM only. In Node.js (version 12.20+, 14.14+, or 16.0+), install with npm:

npm install mdast-util-to-markdown

In Deno with esm.sh:

import {toMarkdown} from 'https://esm.sh/mdast-util-to-markdown@1'

In browsers with esm.sh:

<script type="module">
  import {toMarkdown} from 'https://esm.sh/mdast-util-to-markdown@1?bundle'
</script>

Say our module example.js looks as follows:

import {toMarkdown} from 'mdast-util-to-markdown'

/** @type {import('mdast').Root} */
const tree = {
  type: 'root',
  children: [
    {
      type: 'blockquote',
      children: [
        {type: 'thematicBreak'},
        {
          type: 'paragraph',
          children: [
            {type: 'text', value: '- a\nb !'},
            {
              type: 'link',
              url: 'example.com',
              children: [{type: 'text', value: 'd'}]
            }
          ]
        }
      ]
    }
  ]
}

console.log(toMarkdown(tree))

…now running node example.js yields:

> ***
>
> \- a
> b \![d](example.com)

👉 Note: observe the properly escaped characters which would otherwise turn into a list and image respectively.

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

Turn an mdast syntax tree into markdown.

Marker to use for bullets of items in unordered lists ('*', '+', or '-', default: '*').

Marker to use in certain cases where the primary bullet doesn’t work ('*', '+', or '-', default: depends).

There are three cases where the primary bullet can’t be used:

• When three list items are on their own, the last one is empty, and bullet is also a valid rule: * - +. This would turn into a thematic break if serialized with three primary bullets. As this is an edge case unlikely to appear in normal markdown, the last list item will be given a different bullet.
• When a thematic break is the first child of one of the list items, and bullet is the same character as rule: - ***. This would turn into a single thematic break if serialized with primary bullets. As this is an edge case unlikely to appear in normal markdown this markup is always fixed, even if bulletOther is not passed
• When two unordered lists appear next to each other: * a\n- b. CommonMark sees different bullets as different lists, but several markdown parsers parse it as one list. To solve for both, we instead inject an empty comment between the two lists: * a\n<!---->\n* b, but if bulletOther is given explicitly, it will be used instead

Marker to use for bullets of items in ordered lists ('.' or ')', default: '.').

Marker to use in certain cases where the primary bullet for ordered items doesn’t work ('.' or ')', default: none).

There is one case where the primary bullet for ordered items can’t be used:

• When two ordered lists appear next to each other: 1. a\n2) b. CommonMark added support for ) as a marker, but other markdown parsers do not support it. To solve for both, we instead inject an empty comment between the two lists: 1. a\n<!---->\n1. b, but if bulletOrderedOther is given explicitly, it will be used instead

Whether to add the same number of number signs (#) at the end of an ATX heading as the opening sequence (boolean, default: false).

Marker to use for emphasis ('*' or '_', default: '*').

Marker to use for fenced code ('`' or '~', default: '`').

Whether to use fenced code always (boolean, default: false). The default is to use fenced code if there is a language defined, if the code is empty, or if it starts or ends in blank lines.

Whether to increment the counter of ordered lists items (boolean, default: true).

How to indent the content of list items ('one', 'tab', or 'mixed', default: 'tab'). Either with the size of the bullet plus one space (when 'one'), a tab stop ('tab'), or depending on the item and its parent list ('mixed', uses 'one' if the item and list are tight and 'tab' otherwise).

Marker to use for titles ('"' or "'", default: '"').

Whether to always use resource links (boolean, default: false). The default is to use autolinks (<https://example.com>) when possible and resource links ([text](url)) otherwise.

Marker to use for thematic breaks ('*', '-', or '_', default: '*').

Number of markers to use for thematic breaks (number, default: 3, min: 3).

Whether to add spaces between markers in thematic breaks (boolean, default: false).

Whether to use setext headings when possible (boolean, default: false). The default is to always use ATX headings (# heading) instead of setext headings (heading\n=======). Setext headings can’t be used for empty headings or headings with a rank of three or more.

Marker to use for strong ('*' or '_', default: '*').

Whether to join definitions without a blank line (boolean, default: false). The default is to add blank lines between any flow (“block”) construct. Turning this option on is a shortcut for a join function like so:

function joinTightDefinitions(left, right) {
  if (left.type === 'definition' && right.type === 'definition') {
    return 0
  }
}

Object mapping node types to custom handlers (Record<string, Handle>, default: {}). Useful for syntax extensions.

This option is a bit advanced. It’s recommended to look at the code in lib/handle/ for examples.

List of functions used to determine what to place between two flow nodes (Array<Join>, default: []).

“Blocks” are typically joined by one blank line. Sometimes it’s nicer to have them flush next to each other, yet other times they can’t occur together at all. Join functions receive two adjacent siblings and their parent and can return number or boolean, to signal how many blank lines to use between them. A return value of true is as passing 1. A return value of false means the nodes cannot be joined by a blank line, such as two adjacent block quotes or indented code after a list, in which case a comment will be injected to break them up:

> Quote 1

<!---->

> Quote 2

List of patterns to escape (Array<Unsafe>). Useful for syntax extensions.

This option is quite advanced. It’s recommended to look at the code in lib/unsafe.js for examples.

List of extensions (Array<ToMarkdownExtension>, default: []). Each ToMarkdownExtension is an object with the same interface as options here.

Serialized markdown (string).

• syntax-tree/mdast-util-directive — directives
• syntax-tree/mdast-util-frontmatter — frontmatter (YAML, TOML, more)
• syntax-tree/mdast-util-gfm — GFM
• syntax-tree/mdast-util-gfm-autolink-literal — GFM autolink literals
• syntax-tree/mdast-util-gfm-footnote — GFM footnotes
• syntax-tree/mdast-util-gfm-strikethrough — GFM strikethrough
• syntax-tree/mdast-util-gfm-table — GFM tables
• syntax-tree/mdast-util-gfm-task-list-item — GFM task list items
• syntax-tree/mdast-util-math — math
• syntax-tree/mdast-util-mdx — MDX
• syntax-tree/mdast-util-mdx-expression — MDX expressions
• syntax-tree/mdast-util-mdx-jsx — MDX JSX
• syntax-tree/mdast-util-mdxjs-esm — MDX ESM

Markdown is serialized according to CommonMark but care is taken to format in such a way that the resulting markdown should work with most markdown parsers. Extensions can add support for custom syntax.

The syntax tree is mdast.

This package is fully typed with TypeScript. It exports the additional types Options, Map, Unsafe, Join, Handlers, Handle, Context, SafeOptions, which model the interfaces used by options and extensions.

mdast-util-to-markdown will do its best to serialize markdown to match the syntax tree, but there are several cases where that is impossible. It’ll do its best, but complete roundtripping is impossible given that any value could be injected into the tree.

As markdown is sometimes used for HTML, and improper use of HTML can open you up to a cross-site scripting (XSS) attack, use of mdast-util-to-markdown and parsing it again later could potentially be unsafe. When parsing markdown afterwards and then going to HTML, use something like hast-util-sanitize to make the tree safe.

• syntax-tree/mdast-util-from-markdown — parse markdown to mdast
• micromark/micromark — parse markdown
• remarkjs/remark — process markdown

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.

MIT © Titus Wormer