Project: micromark/micromark-extension-mdxjs-esm

Package: micromark-extension-mdxjs-esm@0.3.1

  1. Dependencies: 3·Dependents: 1
  2. micromark extension to support MDX JS import/exports
  1. unified 169
  2. markdown 142
  3. mdx 29
  4. javascript 17
  5. micromark 16
  6. micromark-extension 16
  7. mdxjs 8
  8. ecmascript 7
  9. js 5
  10. export 4
  11. es 3
  12. import 2


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micromark extension to support MDX.js ESM import/exports.

This package provides the low-level modules for integrating with the micromark tokenizer but has no handling of compiling to HTML: go to a syntax tree instead.

You should probably use this with mdast-util-mdxjs-esm (mdast). Or use micromark-extension-mdxjs and mdast-util-mdx instead, which includes both, to support all of MDX.js. Or, use those through remark-mdx (remark).



npm install micromark-extension-mdxjs-esm


See mdast-util-mdxjs-esm for an example.



Support ESM imports and exports of MDX.

The export of syntax is a function that can be called with options and returns an extension for the micromark parser (to tokenize import/exports; can be passed in extensions).


Acorn parser to use (Acorn, required).


Options to pass to acorn (Object, default: {ecmaVersion: 2020, locations: true, sourceType: 'module'}). All fields except for locations can be set.


Whether to add an estree field to mdxjsEsm tokens with results from acorn (boolean, default: false).


All valid imports and exports are supported, depending on what the given acorn instance and configuration supports.

When the lowercase strings export or import are found, followed by unicode whitespace (\s), we expect JavaScript. Otherwise, like normal in markdown, we exit and it’ll end up as a paragraph. We continue parsing until we find a line ending followed by a blank line. At that point, we parse with acorn: it if parses, we found our block. Otherwise, if parsing failed at the last character, we assume it’s a blank line in code: we continue on until the next blank line and try again. Otherwise, the acorn error is thrown.

import a from "b"
import * as a from "b"
import {a} from "b"
import {a as b} from "c"
import a, {b as c} from "d"
import a, * as b from "c"
import "a"

export var a = ""
export const a = ""
export let a = ""
export var a, b
export var a = "a", b = "b"
export function a() {}
export class a {}
export var {a} = {}
export var {a: b} = {}
export var [a] = []
export default a = 1
export default function a() {}
export default class a {}
export * from "a"
export * as a from "b"
export {a} from "b"
export {a as b} from "c"
export {default} from "b"
export {default as a, b} from "c"

{/* Blank lines are supported in expressions: */}

export function a() {

  return "b"


{/* A blank line must be used after import/exports: this is incorrect! */}

import a from "b"
## Hello, world!


Could not parse import/exports with acorn: $error

This error occurs if acorn crashes (source: micromark-extension-mdxjs-esm, rule id: acorn). For example:

import 1/1

Unexpected $type in code: only import/exports are supported

This error occurs when a non-ESM construct is found (source: micromark-extension-mdxjs-esm, rule id: non-esm). For example:

export var a = 1
var b


An mdxjsEsm token is used to reflect the block of import/exports in markdown.

It includes:


See contributing.md in micromark/.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