mdast extension to parse and serialize MDX.js ESM (import/exports)

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mdast extensions to parse and serialize MDX ESM (import/exports).


*   [`mdxjsEsmFromMarkdown`](#mdxjsesmfrommarkdown)
*   [`mdxjsEsmToMarkdown`](#mdxjsesmtomarkdown)
*   [`MdxjsEsm`](#mdxjsesm)
*   [`MdxjsEsmHast`](#mdxjsesmhast)
*   [Nodes](#nodes)
*   [Content model](#content-model)

What is this?

This package contains two extensions that add support for MDX ESM syntax in markdown to mdast. These extensions plug into mdast-util-from-markdownmdast-util-from-markdown (to support parsing ESM in markdown into a syntax tree) and mdast-util-to-markdownmdast-util-to-markdown (to support serializing ESM in syntax trees to markdown).

When to use this

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-mdxjs-esmextension.
When you are working with syntax trees and want all of MDX, use mdast-util-mdxmdast-util-mdx instead.
All these packages are used in remark-mdxremark-mdx, which focusses on making it easier to transform content by abstracting these internals away.


This package is ESM onlyesm. In Node.js (version 14.14+ and 16.0+), install with npm:
npm install mdast-util-mdxjs-esm

In Deno with esm.shesmsh:
import {mdxjsEsmFromMarkdown, mdxjsEsmToMarkdown} from ''

In browsers with esm.shesmsh:
<script type="module">
  import {mdxjsEsmFromMarkdown, mdxjsEsmToMarkdown} from ''


Say our document example.mdx contains:
import a from 'b'
export const c = ''


…and our module example.js looks as follows:
import fs from 'node:fs/promises'
import * as acorn from 'acorn'
import {fromMarkdown} from 'mdast-util-from-markdown'
import {toMarkdown} from 'mdast-util-to-markdown'
import {mdxjsEsm} from 'micromark-extension-mdxjs-esm'
import {mdxjsEsmFromMarkdown, mdxjsEsmToMarkdown} from 'mdast-util-mdxjs-esm'

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

const tree = fromMarkdown(doc, {
  extensions: [mdxjsEsm({acorn, addResult: true})],
  mdastExtensions: [mdxjsEsmFromMarkdown]


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


…now running node example.js yields (positional info removed for brevity):
  type: 'root',
  children: [
      type: 'mdxjsEsm',
      value: "import a from 'b'\nexport const c = ''",
      data: {
        estree: {
          type: 'Program',
          body: [
              type: 'ImportDeclaration',
              specifiers: [
                  type: 'ImportDefaultSpecifier',
                  local: {type: 'Identifier', name: 'a'}
              source: {type: 'Literal', value: 'b', raw: "'b'"}
              type: 'ExportNamedDeclaration',
              declaration: {
                type: 'VariableDeclaration',
                declarations: [
                    type: 'VariableDeclarator',
                    id: {type: 'Identifier', name: 'c'},
                    init: {type: 'Literal', value: '', raw: "''"}
                kind: 'const'
              specifiers: [],
              source: null
          sourceType: 'module'
    {type: 'paragraph', children: [{type: 'text', value: 'd'}]}

import a from 'b'
export const c = ''



This package exports the identifiers mdxjsEsmFromMarkdownapi-mdxjs-esm-from-markdown and mdxjsEsmToMarkdownapi-mdxjs-esm-to-markdown. There is no default export.


Extension for mdast-util-from-markdownmdast-util-from-markdown to enable MDX ESM.
When using the micromark syntax extensionextension with addResult, nodes will have a data.estree field set to an ESTree Programprogram node.


Extension for mdast-util-to-markdownmdast-util-to-markdown to enable MDX ESM.


MDX ESM (import/export) node (TypeScript type).
import type {Program} from 'estree-jsx'
import type {Literal} from 'mdast'

interface MdxjsEsm extends Literal {
  type: 'mdxjsEsm'
  data?: {estree?: Program | null | undefined}


Same as MdxjsEsmapi-mdxjs-esm, but registered with @types/hast (TypeScript type).
import type {Program} from 'estree-jsx'
import type {Literal} from 'hast'

interface MdxjsEsm extends Literal {
  type: 'mdxjsEsm'
  data?: {estree?: Program | null | undefined}


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


See Syntax in micromark-extension-mdxjs-esmsyntax.

Syntax tree

The following interfaces are added to mdast by this utility.



interface MdxjsEsm <: Literal {
  type: 'mdxjsEsm'

MdxjsEsm (Literaldfn-literal) represents ESM import/exports embedded in MDX. It can be used where flowdfn-flow-content content is expected. Its content is represented by its value field.
For example, the following Markdown:
import a from 'b'

  type: 'mdxjsEsm',
  value: 'import a from \'b\''

Content model

FlowContent (MDX.js ESM)

type FlowContentMdxjsEsm = MdxjsEsm | FlowContent

Note that when ESM is present, it can only exist as top-level content: if it has a parent
dfn-parent, that parent must be Rootdfn-root.


This package is fully typed with TypeScript
. It exports the additional types MdxjsEsmapi-mdxjs-esm and MdxjsEsmHastapi-mdxjs-esm-hast.
It also registers the node type 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-mdxjs-esm')}

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

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

visit(tree, (node) => {
  // `node` can now be an 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 plugin works with mdast-util-from-markdown version 1+ and mdast-util-to-markdown version 1+.


— remark plugin to support MDX
— mdast utility to support MDX
— micromark extension to parse MDX.js ESM


See contributing.mdcontributing in syntax-tree/.githubhealth for ways to get started. See support.mdsupport for ways to get help.
This project has a code of conductcoc. By interacting with this repository, organization, or community you agree to abide by its terms.


MITlicense © Titus Wormerauthor