mdast extensions to parse and serialize MDX: ESM, JSX, and expressions.

• What is this?
• When to use this
• Install
• Use
• API
  • mdxFromMarkdown()
  • mdxToMarkdown(options?)
  • ToMarkdownOptions
• HTML
• Syntax
• Syntax tree
• Types
• Compatibility
• Related
• Contribute
• License

This package contains two extensions that add support for MDX syntax in markdown to mdast: ESM (import x from 'y'), JSX (<a />), and expressions ({Math.PI}). These extensions plug into mdast-util-from-markdown (to support parsing MDX in markdown into a syntax tree) and mdast-util-to-markdown (to support serializing MDX in syntax trees to markdown).

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-mdx or micromark-extension-mdxjs.

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

• mdast-util-mdx-expression — support MDX expressions
• mdast-util-mdx-jsx — support MDX JSX
• mdast-util-mdxjs-esm — support MDX ESM

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

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

npm install mdast-util-mdx

In Deno with esm.sh:

import {mdxFromMarkdown, mdxToMarkdown} from 'https://esm.sh/mdast-util-mdx@2'

In browsers with esm.sh:

<script type="module">
  import {mdxFromMarkdown, mdxToMarkdown} from 'https://esm.sh/mdast-util-mdx@2?bundle'
</script>

Say our document example.mdx contains:

import Box from "place"

Here’s an expression:

{
  1 + 1 /* } */
}

Which you can also put inline: {1+1}.

<Box>
  <SmallerBox>
    - Lists, which can be indented.
  </SmallerBox>
</Box>

…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 {mdxjs} from 'micromark-extension-mdxjs'
import {mdxFromMarkdown, mdxToMarkdown} from 'mdast-util-mdx'

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

const tree = fromMarkdown(doc, {
  extensions: [mdxjs()],
  mdastExtensions: [mdxFromMarkdown()]
})

console.log(tree)

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

console.log(out)

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

{
  type: 'root',
  children: [
    {
      type: 'mdxjsEsm',
      value: 'import Box from "place"',
      data: {
        estree: {
          type: 'Program',
          body: [
            {
              type: 'ImportDeclaration',
              specifiers: [
                {
                  type: 'ImportDefaultSpecifier',
                  local: {type: 'Identifier', name: 'Box'}
                }
              ],
              source: {type: 'Literal', value: 'place', raw: '"place"'}
            }
          ],
          sourceType: 'module'
        }
      }
    },
    {
      type: 'paragraph',
      children: [{type: 'text', value: 'Here’s an expression:'}]
    },
    {
      type: 'mdxFlowExpression',
      value: '\n1 + 1 /* } */\n',
      data: {
        estree: {
          type: 'Program',
          body: [
            {
              type: 'ExpressionStatement',
              expression: {
                type: 'BinaryExpression',
                left: {type: 'Literal', value: 1, raw: '1'},
                operator: '+',
                right: {type: 'Literal', value: 1, raw: '1'}
              }
            }
          ],
          sourceType: 'module'
        }
      }
    },
    {
      type: 'paragraph',
      children: [
        {type: 'text', value: 'Which you can also put inline: '},
        {
          type: 'mdxTextExpression',
          value: '1+1',
          data: {
            estree: {
              type: 'Program',
              body: [
                {
                  type: 'ExpressionStatement',
                  expression: {
                    type: 'BinaryExpression',
                    left: {type: 'Literal', value: 1, raw: '1'},
                    operator: '+',
                    right: {type: 'Literal', value: 1, raw: '1'}
                  }
                }
              ],
              sourceType: 'module'
            }
          }
        },
        {type: 'text', value: '.'}
      ]
    },
    {
      type: 'mdxJsxFlowElement',
      name: 'Box',
      attributes: [],
      children: [
        {
          type: 'mdxJsxFlowElement',
          name: 'SmallerBox',
          attributes: [],
          children: [
            {
              type: 'list',
              ordered: false,
              start: null,
              spread: false,
              children: [
                {
                  type: 'listItem',
                  spread: false,
                  checked: null,
                  children: [
                    {
                      type: 'paragraph',
                      children: [
                        {type: 'text', value: 'Lists, which can be indented.'}
                      ]
                    }
                  ]
                }
              ]
            }
          ]
        }
      ]
    }
  ]
}

import Box from "place"

Here’s an expression:

{
  1 + 1 /* } */
}

Which you can also put inline: {1+1}.

<Box>
  <SmallerBox>
    *   Lists, which can be indented.
  </SmallerBox>
</Box>

This package exports the identifiers mdxFromMarkdown and mdxToMarkdown. There is no default export.

Create an extension for mdast-util-from-markdown to enable MDX (ESM, JSX, expressions).

Extension for mdast-util-from-markdown to enable MDX (FromMarkdownExtension).

When using the syntax extensions with addResult, ESM and expression nodes will have data.estree fields set to ESTree Program node.

Create an extension for mdast-util-to-markdown to enable MDX (ESM, JSX, expressions).

Extension for mdast-util-to-markdown.

• options (ToMarkdownOptions) — configuration

Extension for mdast-util-to-markdown to enable MDX (FromMarkdownExtension).

Configuration (TypeScript type).

• quote ('"' or "'", default: '"') — preferred quote to use around attribute values
• quoteSmart (boolean, default: false) — use the other quote if that results in less bytes
• tightSelfClosing (boolean, default: false) — do not use an extra space when closing self-closing elements: <img/> instead of <img />
• printWidth (number, default: Infinity) — try and wrap syntax at this width. When set to a finite number (say, 80), the formatter will print attributes on separate lines when a tag doesn’t fit on one line. The normal behavior is to print attributes with spaces between them instead of line endings

MDX has no representation in HTML. Though, when you are dealing with MDX, you will likely go through hast. You can enable passing MDX through to hast by configuring mdast-util-to-hast with passThrough: ['mdxjsEsm', 'mdxFlowExpression', 'mdxJsxFlowElement', 'mdxJsxTextElement', 'mdxTextExpression'].

See Syntax in micromark-extension-mdxjs.

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

• mdast-util-mdx-expression — support MDX expressions
• mdast-util-mdx-jsx — support MDX JSX
• mdast-util-mdxjs-esm — support MDX ESM

This package is fully typed with TypeScript. It exports the additional types MdxFlowExpression, MdxTextExpression, MdxjsEsm, MdxJsxAttributeValueExpression, MdxJsxAttribute, MdxJsxExpressionAttribute, MdxJsxFlowElement, MdxJsxTextElement, and ToMarkdownOptions.

It also registers the node types with @types/mdast and @types/hast. If you’re working with the syntax tree, make sure to import this utility somewhere in your types, as that registers the new node types in the tree.

/**
 * @typedef {import('mdast-util-mdx')}
 */

import {visit} from 'unist-util-visit'

/** @type {import('mdast').Root} */
const tree = getMdastNodeSomeHow()

visit(tree, (node) => {
  // `node` can now be an expression, JSX, or ESM node.
})

Projects maintained by the unified collective are compatible with all maintained versions of Node.js. As of now, that is Node.js 14.14+ and 16.0+. Our projects sometimes work with older versions, but this is not guaranteed.

This utility works with mdast-util-from-markdown version 1+ and mdast-util-to-markdown version 1+.

• remark-mdx — remark plugin to support MDX
• micromark-extension-mdx — micromark extension to parse MDX
• micromark-extension-mdxjs — micromark extension to parse JavaScript-aware MDX

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