mdast-util-mdx-expression

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[mdast][] extensions to parse and serialize [MDX][] expressions ({Math.PI}).

Contents

* What is this?
* When to use this
* Install
* Use
* API
* mdxExpressionFromMarkdown()
* mdxExpressionToMarkdown()
* MdxFlowExpression
* MdxTextExpression
* MdxFlowExpressionHast
* MdxTextExpressionHast
* HTML
* Syntax
* Syntax tree
* Nodes
* Content model
* Types
* Compatibility
* Related
* Contribute
* License

What is this?

This package contains two extensions that add support for MDX expression syntax
in markdown to [mdast][].
These extensions plug into
[mdast-util-from-markdown][mdast-util-from-markdown] (to support parsing
expressions in markdown into a syntax tree) and
[mdast-util-to-markdown][mdast-util-to-markdown] (to support serializing
expressions 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-mdx-expression][extension].

When you are working with syntax trees and want all of MDX, use
[mdast-util-mdx][mdast-util-mdx] instead.

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

Install

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

``sh
npm install mdast-util-mdx-expression
`

In Deno with [esm.sh][esmsh]:

`js
import {mdxExpressionFromMarkdown, mdxExpressionToMarkdown} from 'https://esm.sh/mdast-util-mdx-expression@2'
`

In browsers with [esm.sh][esmsh]:

`html

`

Use

Say our document example.mdx contains:

`mdx
{
a + 1
}

b {true}.
`

…and our module example.js looks as follows:

`js
import fs from 'node:fs/promises'
import * as acorn from 'acorn'
import {mdxExpression} from 'micromark-extension-mdx-expression'
import {fromMarkdown} from 'mdast-util-from-markdown'
import {mdxExpressionFromMarkdown, mdxExpressionToMarkdown} from 'mdast-util-mdx-expression'
import {toMarkdown} from 'mdast-util-to-markdown'

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

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

console.log(tree)

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

console.log(out)
`

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

`js
{
type: 'root',
children: [
{
type: 'mdxFlowExpression',
value: '\na + 1\n',
data: {
estree: {
type: 'Program',
body: [
{
type: 'ExpressionStatement',
expression: {
type: 'BinaryExpression',
left: {type: 'Identifier', name: 'a'},
operator: '+',
right: {type: 'Literal', value: 1, raw: '1'}
}
}
],
sourceType: 'module'
}
}
},
{
type: 'paragraph',
children: [
{type: 'text', value: 'b '},
{
type: 'mdxTextExpression',
value: 'true',
data: {
estree: {
type: 'Program',
body: [
{
type: 'ExpressionStatement',
expression: {type: 'Literal', value: true, raw: 'true'}
}
],
sourceType: 'module'
}
}
},
{type: 'text', value: '.'}
]
}
]
}
`

`markdown
{
a + 1
}

b {true}.
`

API

This package exports the identifiers
[mdxExpressionFromMarkdown][api-mdx-expression-from-markdown] and
[mdxExpressionToMarkdown][api-mdx-expression-to-markdown].
There is no default export.

$3

Create an extension for [mdast-util-from-markdown][mdast-util-from-markdown]
to enable MDX expressions in markdown.

When using the [micromark syntax extension][extension] with addResult, nodes
will have a data.estree field set to an ESTree [Program][program] node.

###### Returns

Extension for mdast-util-from-markdown to enable MDX expressions
([FromMarkdownExtension][from-markdown-extension]).

$3

Create an extension for [mdast-util-to-markdown][mdast-util-to-markdown]
to enable MDX expressions in markdown.

###### Returns

Extension for mdast-util-to-markdown to enable MDX expressions
([ToMarkdownExtension][to-markdown-extension]).

$3

MDX expression node, occurring in flow (block) (TypeScript type).

###### Type

`ts
import type {Program} from 'estree-jsx'
import type {Data, Literal} from 'mdast'

interface MdxFlowExpression extends Literal {
type: 'mdxFlowExpression'
data?: MdxFlowExpressionData | undefined
}

interface MdxFlowExpressionData extends Data {
estree?: Program | null | undefined
}
`

$3

MDX expression node, occurring in text (block) (TypeScript type).

###### Type

`ts
import type {Program} from 'estree-jsx'
import type {Data, Literal} from 'mdast'

interface MdxTextExpression extends Literal {
type: 'mdxTextExpression'
data?: MdxTextExpressionData | undefined
}

interface MdxTextExpressionData extends Data {
estree?: Program | null | undefined
}
`

$3

Same as [MdxFlowExpression][api-mdx-flow-expression], but registered with
@types/hast (TypeScript type).

###### Type

`ts
import type {Program} from 'estree-jsx'
import type {Data, Literal} from 'hast'

interface MdxFlowExpressionHast extends Literal {
type: 'mdxFlowExpression'
data?: MdxFlowExpressionData | undefined
}

interface MdxFlowExpressionData extends Data {
estree?: Program | null | undefined
}
`

$3

Same as [MdxTextExpression][api-mdx-text-expression], but registered with
@types/hast (TypeScript type).

###### Type

`ts
import type {Program} from 'estree-jsx'
import type {Data, Literal} from 'hast'

interface MdxTextExpressionHast extends Literal {
type: 'mdxTextExpression'
data?: MdxTextExpressionData | undefined
}

interface MdxTextExpressionData extends Data {
estree?: Program | null | undefined
}
`

HTML

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

Syntax

See [Syntax in micromark-extension-mdx-expression][syntax].

Syntax tree

The following interfaces are added to [mdast][] by this utility.

$3

#### MdxFlowExpression

`idl
interface MdxFlowExpression <: Literal {
type: 'mdxFlowExpression'
}
`

MdxFlowExpression ([Literal][dfn-literal]) represents a JavaScript
expression embedded in flow (block).
It can be used where [flow][dfn-flow-content] content is expected.
Its content is represented by its value field.

For example, the following markdown:

`markdown
{
1 + 1
}
`

Yields:

`js
{type: 'mdxFlowExpression', value: '\n1 + 1\n'}
`

#### MdxTextExpression

`idl
interface MdxTextExpression <: Literal {
type: 'mdxTextExpression"
}
`

MdxTextExpression ([Literal][dfn-literal]) represents a JavaScript
expression embedded in text (span, inline).
It can be used where [phrasing][dfn-phrasing-content] content is expected.
Its content is represented by its value field.

For example, the following markdown:

`markdown
a {1 + 1} b.
`

Yields:

`js
{type: 'mdxTextExpression', value: '1 + 1'}
`

$3

#### FlowContent (MDX expression)

`idl
type FlowContentMdxExpression = MdxFlowExpression | FlowContent
`

#### PhrasingContent (MDX expression)

`idl
type PhrasingContentMdxExpression = MdxTextExpression | PhrasingContent
`

Types

This package is fully typed with [TypeScript][].
It exports the additional types [MdxFlowExpression][api-mdx-flow-expression],
[MdxFlowExpressionHast][api-mdx-flow-expression-hast],
[MdxTextExpression][api-mdx-text-expression], and
[MdxTextExpressionHast][api-mdx-text-expression-hast].

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.

`js
/**
* @import {} from 'mdast-util-mdx-expression'
* @import {Root} from 'mdast'
*/

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

/* @type {Root} /
const tree = getMdastNodeSomeHow()

visit(tree, function (node) {
// node can now be an expression node.
})
`

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,
mdast-util-mdx-expression@^2, compatible with Node.js 16.

This utility works with mdast-util-from-markdown version 2+ and
mdast-util-to-markdown version 2+.

Related

* [remarkjs/remark-mdx][remark-mdx]
— remark plugin to support MDX
* [syntax-tree/mdast-util-mdx][mdast-util-mdx]
— mdast utility to support MDX
* [micromark/micromark-extension-mdx-expression][extension]
— micromark extension to parse MDX expressions

Contribute

See [contributing.md][contributing] in [syntax-tree/.github][health] for
ways to get started.
See [support.md`][support] for ways to get help.

This project has a [code of conduct][coc].
By interacting with this repository, organization, or community you agree to
abide by its terms.

License

[MIT][license] © [Titus Wormer][author]

[build-badge]: https://github.com/syntax-tree/mdast-util-mdx-expression/workflows/main/badge.svg

[build]: https://github.com/syntax-tree/mdast-util-mdx-expression/actions

[coverage-badge]: https://img.shields.io/codecov/c/github/syntax-tree/mdast-util-mdx-expression.svg

[coverage]: https://codecov.io/github/syntax-tree/mdast-util-mdx-expression

[downloads-badge]: https://img.shields.io/npm/dm/mdast-util-mdx-expression.svg

[downloads]: https://www.npmjs.com/package/mdast-util-mdx-expression

[size-badge]: https://img.shields.io/badge/dynamic/json?label=minzipped%20size&query=$.size.compressedSize&url=https://deno.bundlejs.com/?q=mdast-util-mdx-expression

[size]: https://bundlejs.com/?q=mdast-util-mdx-expression

[sponsors-badge]: https://opencollective.com/unified/sponsors/badge.svg

[backers-badge]: https://opencollective.com/unified/backers/badge.svg

[collective]: https://opencollective.com/unified

[chat-badge]: https://img.shields.io/badge/chat-discussions-success.svg

[chat]: https://github.com/syntax-tree/unist/discussions

[npm]: https://docs.npmjs.com/cli/install

[esm]: https://gist.github.com/sindresorhus/a39789f98801d908bbc7ff3ecc99d99c

[esmsh]: https://esm.sh

[typescript]: https://www.typescriptlang.org

[license]: license

[author]: https://wooorm.com

[health]: https://github.com/syntax-tree/.github

[contributing]: https://github.com/syntax-tree/.github/blob/main/contributing.md

[support]: https://github.com/syntax-tree/.github/blob/main/support.md

[coc]: https://github.com/syntax-tree/.github/blob/main/code-of-conduct.md

[mdast]: https://github.com/syntax-tree/mdast

[mdast-util-to-hast]: https://github.com/syntax-tree/mdast-util-to-hast

[mdast-util-from-markdown]: https://github.com/syntax-tree/mdast-util-from-markdown

[mdast-util-to-markdown]: https://github.com/syntax-tree/mdast-util-to-markdown

[mdast-util-mdx]: https://github.com/syntax-tree/mdast-util-mdx

[extension]: https://github.com/micromark/micromark-extension-mdx-expression

[syntax]: https://github.com/micromark/micromark-extension-mdx-expression#syntax

[program]: https://github.com/estree/estree/blob/master/es2015.md#programs

[dfn-literal]: https://github.com/syntax-tree/mdast#literal

[remark-mdx]: https://mdxjs.com/packages/remark-mdx/

[mdx]: https://mdxjs.com

[from-markdown-extension]: https://github.com/syntax-tree/mdast-util-from-markdown#extension

[to-markdown-extension]: https://github.com/syntax-tree/mdast-util-to-markdown#options

[api-mdx-expression-from-markdown]: #mdxexpressionfrommarkdown

[api-mdx-expression-to-markdown]: #mdxexpressiontomarkdown

[api-mdx-flow-expression]: #mdxflowexpression

[api-mdx-text-expression]: #mdxtextexpression

[api-mdx-flow-expression-hast]: #mdxflowexpressionhast

[api-mdx-text-expression-hast]: #mdxtextexpressionhast

[dfn-flow-content]: #flowcontent-mdx-expression

[dfn-phrasing-content]: #phrasingcontent-mdx-expression