micromark-extension-mdxjs-esm

What is micromark-extension-mdxjs-esm?

The micromark-extension-mdxjs-esm package is an extension for the micromark Markdown parser that adds support for parsing MDX.js (Markdown for the component era). It allows users to use JSX within their Markdown documents, enabling the embedding of React components and other JSX elements.

What are micromark-extension-mdxjs-esm's main functionalities?

Parsing MDX syntax

This feature allows the parsing of MDX syntax within Markdown content. The code sample demonstrates how to use the micromark parser with the mdxjs extension to parse a string containing an MDX component.

import {micromark} from 'micromark';
import {mdxjs} from 'micromark-extension-mdxjs-esm';

const output = micromark('<MyComponent />', {
extensions: [mdxjs()]
});

Support for JSX

This feature enables the use of JSX within Markdown documents. The code sample shows how to parse a Markdown string that includes a JSX component with a prop.

import {micromark} from 'micromark';
import {mdxjs} from 'micromark-extension-mdxjs-esm';

const output = micromark('# Hello, world!\n\n<MyComponent prop1={value} />', {
extensions: [mdxjs()]
});

Other packages similar to micromark-extension-mdxjs-esm

remark-mdx

remark-mdx is a plugin for the remark Markdown processor that adds support for MDX. It is similar to micromark-extension-mdxjs-esm in that it allows for MDX syntax in Markdown files, but it is built on top of the remark ecosystem.

unified

unified is an interface for parsing, transforming, and serializing content through syntax trees and is often used with remark and rehype plugins. While not specific to MDX, it can be used in conjunction with other plugins to achieve similar functionality to micromark-extension-mdxjs-esm.

README

micromark-extension-mdxjs-esm

micromark extension to support MDX ESM (import x from 'y').

Contents

• What is this?
• When to use this
• Install
• Use
• API
  • mdxjsEsm(options)
  • Options
• Authoring
• Syntax
• Errors
  • Could not parse import/exports with acorn
  • Unexpected $type in code: only import/exports are supported
• Tokens
• Types
• Compatibility
• Security
• Related
• Contribute
• License

What is this?

This package contains an extension that adds support for the ESM syntax enabled by MDX to micromark. These extensions are used inside MDX. It matches how imports and exports work in JavaScript through acorn.

This package is aware of JavaScript syntax.

When to use this

This project is useful when you want to support ESM in markdown.

You can use this extension when you are working with micromark. To support all MDX features, use micromark-extension-mdxjs instead.

When you need a syntax tree, combine this package with mdast-util-mdxjs-esm.

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

When you are using mdx-js/mdx, all of this is already included.

Install

This package is ESM only. In Node.js (version 16+), install with npm:

npm install micromark-extension-mdxjs-esm

In Deno with esm.sh:

import {mdxjsEsm} from 'https://esm.sh/micromark-extension-mdxjs-esm@2'

In browsers with esm.sh:

<script type="module">
  import {mdxjsEsm} from 'https://esm.sh/micromark-extension-mdxjs-esm@2?bundle'
</script>

Use

import {Parser} from 'acorn'
import acornJsx from 'acorn-jsx'
import {micromark} from 'micromark'
import {mdxjsEsm} from 'micromark-extension-mdxjs-esm'

const acorn = Parser.extend(acornJsx())

const output = micromark('import a from "b"\n\n# c', {
  extensions: [mdxjsEsm({acorn})]
})

console.log(output)

Yields:

<h1>c</h1>

…which is useless: go to a syntax tree with mdast-util-from-markdown and mdast-util-mdxjs-esm instead.

API

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

The export map supports the development condition. Run node --conditions development module.js to get instrumented dev code. Without this condition, production code is loaded.

mdxjsEsm(options)

Create an extension for micromark to enable MDX ESM syntax.

Parameters

• options (Options, required) — configuration

Returns

Extension for micromark that can be passed in extensions to enable MDX ESM syntax (Extension).

Options

Configuration (TypeScript type).

Fields

• acorn (Acorn, required) — acorn parser to use
• acornOptions (AcornOptions, default: {ecmaVersion: 2024, locations: true, sourceType: 'module'}) — configuration for acorn; all fields except locations can be set
• addResult (boolean, default: false) — whether to add estree fields to tokens with results from acorn

Authoring

When authoring markdown with ESM, make sure to follow export and import statements with blank lines before more markdown.

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 a space, 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 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.

Some examples of valid export and import statements:

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!

Syntax

ESM forms with the following BNF:

; Restriction: the entire construct must be valid JavaScript.
mdx_esm ::= word ' ' *line *(eol *line)

word ::= 'e' 'x' 'p' 'o' 'r' 't' | 'i' 'm' 'p' 'o' 'r' 't'

This construct must be followed by a blank line or eof (end of file).

Errors

Could not parse import/exports with acorn

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

Tokens

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

It includes:

• lineEnding for the \r, \n, and \r\n
• lineEndingBlank for the same characters but when after potential whitespace and another line ending
• whitespace for markdown spaces and tabs in blank lines
• mdxjsEsmData for any character in a line of mdxjsEsm

Types

This package is fully typed with TypeScript. It exports the additional type Options.

Compatibility

Projects maintained by the unified collective are compatible with maintained versions of Node.js.

When we cut a new major release, we drop support for unmaintained versions of Node. This means we try to keep the current release line, micromark-extension-mdxjs-esm@^2, compatible with Node.js 16.

This package works with micromark version 3 and later.

Security

This package is safe.

Related

• micromark-extension-mdxjs — support all MDX syntax
• mdast-util-mdxjs-esm — support MDX ESM in mdast
• remark-mdx — support all MDX syntax in remark

Contribute

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.

License

MIT © Titus Wormer