mdast-util-to-markdown

What is mdast-util-to-markdown?

The mdast-util-to-markdown package is a utility to serialize Markdown Abstract Syntax Tree (MDAST) nodes to markdown text. It is part of the unified ecosystem and is typically used to convert MDAST, which is an abstract representation of markdown documents, back into markdown format.

What are mdast-util-to-markdown's main functionalities?

Serialize MDAST to Markdown

Converts an MDAST node into a markdown string. This is the core functionality of the package.

const toMarkdown = require('mdast-util-to-markdown');
const mdast = {
  type: 'paragraph',
  children: [{ type: 'text', value: 'Hello, world!' }]
};
const markdown = toMarkdown(mdast);
console.log(markdown); // Outputs: 'Hello, world!'

Customize Handlers

Allows the user to define custom handlers for different types of MDAST nodes, enabling serialization of custom or extended MDAST nodes.

const toMarkdown = require('mdast-util-to-markdown');
const mdast = {
  type: 'customNode',
  value: 'This is custom'
};
const handlers = {
  customNode(node) {
    return `Custom: ${node.value}`;
  }
};
const markdown = toMarkdown(mdast, { handlers });
console.log(markdown); // Outputs: 'Custom: This is custom'

Extensions

Supports extensions to handle syntax from GitHub Flavored Markdown (GFM) and other markdown variants.

const toMarkdown = require('mdast-util-to-markdown');
const gfm = require('mdast-util-gfm');
const mdast = {
  type: 'paragraph',
  children: [{ type: 'text', value: 'Hello, world!' }]
};
const markdown = toMarkdown(mdast, { extensions: [gfm.toMarkdown] });
console.log(markdown); // Outputs: 'Hello, world!' with GFM-specific serialization

Other packages similar to mdast-util-to-markdown

remark-stringify

Part of the remark processor that turns MDAST into markdown. It is similar to mdast-util-to-markdown but is typically used within the remark ecosystem.

rehype-stringify

Part of the rehype processor that turns HAST (Hypertext Abstract Syntax Tree) into HTML. While it operates on a different type of syntax tree, it provides a similar serialization functionality for HTML instead of markdown.

commonmark

A library that provides parsing and rendering of CommonMark Markdown. It offers similar markdown serialization capabilities but is based on the CommonMark specification.

README

mdast-util-to-markdown

mdast utility to parse markdown.

When to use this

Use this if you have direct access to an AST and need to serialize it. Use remark instead, which includes this, but has a nice interface and hundreds of plugins.

Install

This package is ESM only: Node 12+ is needed to use it and it must be imported instead of required.

npm:

npm install mdast-util-to-markdown

Use

Say we have the following script, example.js:

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

var 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 yields (note the properly escaped characters which would otherwise turn into a list and image respectively):

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

API

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

toMarkdown(tree[, options])

Serialize mdast to markdown.

Formatting options

options.bullet

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

options.closeAtx

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

options.emphasis

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

options.fence

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

options.fences

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

options.incrementListMarker

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

options.listItemIndent

Whether to indent the content of list items with the size of the bullet plus one space (when 'one') or 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) ('one', 'tab', or 'mixed', default: 'tab').

options.quote

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

options.resourceLink

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

options.rule

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

options.ruleRepetition

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

options.ruleSpaces

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

options.setext

Whether to use setext headings when possible (boolean, default: false). Setext headings are not possible for headings with a rank more than 2 or when they’re empty.

options.strong

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

options.tightDefinitions

Whether to join definitions w/o a blank line (boolean, default: false). Shortcut for a join function like so:

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

options.handlers

Object mapping node types to custom handlers. Useful for syntax extensions. Take a look at lib/handle for examples.

options.join

List of functions used to determine what to place between two flow nodes. Often, they are joined by one blank line. In certain cases, it’s nicer to have them next to each other. Or, they can’t occur together. These functions receive two adjacent nodes and their parent and can return number or boolean, referring to 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

options.unsafe

List of patterns to escape. Useful for syntax extensions. Take a look at lib/unsafe.js for examples.

Extension options

options.extensions

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

Returns

string — Serialized markdown.

List of extensions

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

Security

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.

Related

• micromark/micromark — the smallest commonmark-compliant markdown parser that exists
• remarkjs/remark — markdown processor powered by plugins
• syntax-tree/mdast-util-from-markdown — parse markdown to mdast

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