unified

Plugin to add support for serializing as HTML.

• @this processor.
• @param Configuration (optional).
• @returns Nothing.

Add support for parsing from markdown.

• @this processor.
• @param Configuration (optional).
• @returns Nothing.

Turn markdown into HTML.

Notes

Signature

• if a processor is given, runs the (rehype) plugins used on it with a hast tree, then discards the result (bridge mode)
• otherwise, returns a hast tree, the plugins used after remarkRehype are rehype plugins (mutate mode)

👉 Note: It’s highly unlikely that you want to pass a processor.

HTML

Raw HTML is available in mdast as html nodes and can be embedded in hast as semistandard raw nodes. Most plugins ignore raw nodes but two notable ones don’t:

• rehype-stringify also has an option allowDangerousHtml which will output the raw HTML. This is typically discouraged as noted by the option name but is useful if you completely trust authors
• rehype-raw can handle the raw embedded HTML strings by parsing them into standard hast nodes (element, text, etc). This is a heavy task as it needs a full HTML parser, but it is the only way to support untrusted content

Footnotes

Many options supported here relate to footnotes. Footnotes are not specified by CommonMark, which we follow by default. They are supported by GitHub, so footnotes can be enabled in markdown with remark-gfm.

The options footnoteBackLabel and footnoteLabel define natural language that explains footnotes, which is hidden for sighted users but shown to assistive technology. When your page is not in English, you must define translated values.

Back references use ARIA attributes, but the section label itself uses a heading that is hidden with an sr-only class. To show it to sighted users, define different attributes in footnoteLabelProperties.

Clobbering

Footnotes introduces a problem, as it links footnote calls to footnote definitions on the page through id attributes generated from user content, which results in DOM clobbering.

DOM clobbering is this:

<p id=x></p>
<script>alert(x) // `x` now refers to the DOM `p#x` element</script>

Elements by their ID are made available by browsers on the window object, which is a security risk. Using a prefix solves this problem.

More information on how to handle clobbering and the prefix is explained in Example: headings (DOM clobbering) in rehype-sanitize.

Unknown nodes

Unknown nodes are nodes with a type that isn’t in handlers or passThrough. The default behavior for unknown nodes is:

• when the node has a value (and doesn’t have data.hName, data.hProperties, or data.hChildren, see later), create a hast text node
• otherwise, create a <div> element (which could be changed with data.hName), with its children mapped from mdast to hast as well

This behavior can be changed by passing an unknownHandler.

• @overload
• @overload
• @param destination Processor or configuration (optional).
• @param options When a processor was given, configuration (optional).
• @returns Transform.

Create a new processor.

• @example This example shows how a new processor can be created (from remark) and linked to stdin(4) and stdout(4).

  import process from 'node:process'
  import concatStream from 'concat-stream'
  import {remark} from 'remark'
  
  process.stdin.pipe(
    concatStream(function (buf) {
      process.stdout.write(String(remark().processSync(buf)))
    })
  )
  

• @returns New unfrozen processor (processor). This processor is configured to work the same as its ancestor. When the descendant processor is configured in the future it does not affect the ancestral processor.

Create a new processor.

• @example This example shows how a new processor can be created (from remark) and linked to stdin(4) and stdout(4).

  import process from 'node:process'
  import concatStream from 'concat-stream'
  import {remark} from 'remark'
  
  process.stdin.pipe(
    concatStream(function (buf) {
      process.stdout.write(String(remark().processSync(buf)))
    })
  )
  

• @returns New unfrozen processor (processor). This processor is configured to work the same as its ancestor. When the descendant processor is configured in the future it does not affect the ancestral processor.

Configure the processor to use a plugin, a list of usable values, or a preset.

If the processor is already using a plugin, the previous plugin configuration is changed based on the options that are passed in. In other words, the plugin is not added a second time.

Note: use cannot be called on frozen processors. Call the processor first to create a new unfrozen processor.

• @example There are many ways to pass plugins to .use(). This example gives an overview:

  import {unified} from 'unified'
  
  unified()
    // Plugin with options:
    .use(pluginA, {x: true, y: true})
    // Passing the same plugin again merges configuration (to `{x: true, y: false, z: true}`):
    .use(pluginA, {y: false, z: true})
    // Plugins:
    .use([pluginB, pluginC])
    // Two plugins, the second with options:
    .use([pluginD, [pluginE, {}]])
    // Preset with plugins and settings:
    .use({plugins: [pluginF, [pluginG, {}]], settings: {position: false}})
    // Settings only:
    .use({settings: {position: false}})
  

• @template {Array} [Parameters=[]]
• @template {Node | string | undefined} [Input=undefined]
• @template [Output=Input]
• @overload
• @overload
• @overload
• @param value Usable value.
• @param parameters Parameters, when a plugin is given as a usable value.
• @returns Current processor.

Add support for parsing from markdown.

• @this processor.
• @param Configuration (optional).
• @returns Nothing.

Configure the processor to use a plugin, a list of usable values, or a preset.

If the processor is already using a plugin, the previous plugin configuration is changed based on the options that are passed in. In other words, the plugin is not added a second time.

Note: use cannot be called on frozen processors. Call the processor first to create a new unfrozen processor.

• @example There are many ways to pass plugins to .use(). This example gives an overview:

  import {unified} from 'unified'
  
  unified()
    // Plugin with options:
    .use(pluginA, {x: true, y: true})
    // Passing the same plugin again merges configuration (to `{x: true, y: false, z: true}`):
    .use(pluginA, {y: false, z: true})
    // Plugins:
    .use([pluginB, pluginC])
    // Two plugins, the second with options:
    .use([pluginD, [pluginE, {}]])
    // Preset with plugins and settings:
    .use({plugins: [pluginF, [pluginG, {}]], settings: {position: false}})
    // Settings only:
    .use({settings: {position: false}})
  

• @template {Array} [Parameters=[]]
• @template {Node | string | undefined} [Input=undefined]
• @template [Output=Input]
• @overload
• @overload
• @overload
• @param value Usable value.
• @param parameters Parameters, when a plugin is given as a usable value.
• @returns Current processor.

Turn markdown into HTML.

Notes

Signature

• if a processor is given, runs the (rehype) plugins used on it with a hast tree, then discards the result (bridge mode)
• otherwise, returns a hast tree, the plugins used after remarkRehype are rehype plugins (mutate mode)

👉 Note: It’s highly unlikely that you want to pass a processor.

HTML

Raw HTML is available in mdast as html nodes and can be embedded in hast as semistandard raw nodes. Most plugins ignore raw nodes but two notable ones don’t:

• rehype-stringify also has an option allowDangerousHtml which will output the raw HTML. This is typically discouraged as noted by the option name but is useful if you completely trust authors
• rehype-raw can handle the raw embedded HTML strings by parsing them into standard hast nodes (element, text, etc). This is a heavy task as it needs a full HTML parser, but it is the only way to support untrusted content

Footnotes

Many options supported here relate to footnotes. Footnotes are not specified by CommonMark, which we follow by default. They are supported by GitHub, so footnotes can be enabled in markdown with remark-gfm.

The options footnoteBackLabel and footnoteLabel define natural language that explains footnotes, which is hidden for sighted users but shown to assistive technology. When your page is not in English, you must define translated values.

Back references use ARIA attributes, but the section label itself uses a heading that is hidden with an sr-only class. To show it to sighted users, define different attributes in footnoteLabelProperties.

Clobbering

Footnotes introduces a problem, as it links footnote calls to footnote definitions on the page through id attributes generated from user content, which results in DOM clobbering.

DOM clobbering is this:

<p id=x></p>
<script>alert(x) // `x` now refers to the DOM `p#x` element</script>

Elements by their ID are made available by browsers on the window object, which is a security risk. Using a prefix solves this problem.

More information on how to handle clobbering and the prefix is explained in Example: headings (DOM clobbering) in rehype-sanitize.

Unknown nodes

Unknown nodes are nodes with a type that isn’t in handlers or passThrough. The default behavior for unknown nodes is:

• when the node has a value (and doesn’t have data.hName, data.hProperties, or data.hChildren, see later), create a hast text node
• otherwise, create a <div> element (which could be changed with data.hName), with its children mapped from mdast to hast as well

This behavior can be changed by passing an unknownHandler.

• @overload
• @overload
• @param destination Processor or configuration (optional).
• @param options When a processor was given, configuration (optional).
• @returns Transform.

Configure the processor to use a plugin, a list of usable values, or a preset.

If the processor is already using a plugin, the previous plugin configuration is changed based on the options that are passed in. In other words, the plugin is not added a second time.

Note: use cannot be called on frozen processors. Call the processor first to create a new unfrozen processor.

• @example There are many ways to pass plugins to .use(). This example gives an overview:

  import {unified} from 'unified'
  
  unified()
    // Plugin with options:
    .use(pluginA, {x: true, y: true})
    // Passing the same plugin again merges configuration (to `{x: true, y: false, z: true}`):
    .use(pluginA, {y: false, z: true})
    // Plugins:
    .use([pluginB, pluginC])
    // Two plugins, the second with options:
    .use([pluginD, [pluginE, {}]])
    // Preset with plugins and settings:
    .use({plugins: [pluginF, [pluginG, {}]], settings: {position: false}})
    // Settings only:
    .use({settings: {position: false}})
  

• @template {Array} [Parameters=[]]
• @template {Node | string | undefined} [Input=undefined]
• @template [Output=Input]
• @overload
• @overload
• @overload
• @param value Usable value.
• @param parameters Parameters, when a plugin is given as a usable value.
• @returns Current processor.

Plugin to add support for serializing as HTML.

• @this processor.
• @param Configuration (optional).
• @returns Nothing.

Process the given file as configured on the processor.

Note: process freezes the processor if not already frozen.

Note: process performs the parse, run, and stringify phases.

• @overload
• @overload
• @param file File (optional); typically string or VFile]; any value accepted as x in new VFile(x).
• @param done Callback (optional).
• @returns Nothing if done is given. Otherwise a promise, rejected with a fatal error or resolved with the processed file. The parsed, transformed, and compiled value is available at file.value (see note).

  Note: unified typically compiles by serializing: most compilers return string (or Uint8Array). Some compilers, such as the one configured with rehype-react, return other values (in this case, a React tree). If you’re using a compiler that doesn’t serialize, expect different result values.

  To register custom results in TypeScript, add them to {@linkcode CompileResultMap}.

The console module provides a simple debugging console that is similar to the JavaScript console mechanism provided by web browsers.

The module exports two specific components:

• A Console class with methods such as console.log(), console.error() and console.warn() that can be used to write to any Node.js stream.
• A global console instance configured to write to process.stdout and process.stderr. The global console can be used without importing the node:console module.

Warning: The global console object's methods are neither consistently synchronous like the browser APIs they resemble, nor are they consistently asynchronous like all other Node.js streams. See the note on process I/O for more information.

Example using the global console:

console.log('hello world');
// Prints: hello world, to stdout
console.log('hello %s', 'world');
// Prints: hello world, to stdout
console.error(new Error('Whoops, something bad happened'));
// Prints error message and stack trace to stderr:
//   Error: Whoops, something bad happened
//     at [eval]:5:15
//     at Script.runInThisContext (node:vm:132:18)
//     at Object.runInThisContext (node:vm:309:38)
//     at node:internal/process/execution:77:19
//     at [eval]-wrapper:6:22
//     at evalScript (node:internal/process/execution:76:60)
//     at node:internal/main/eval_string:23:3

const name = 'Will Robinson';
console.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to stderr

Example using the Console class:

const out = getStreamSomehow();
const err = getStreamSomehow();
const myConsole = new console.Console(out, err);

myConsole.log('hello world');
// Prints: hello world, to out
myConsole.log('hello %s', 'world');
// Prints: hello world, to out
myConsole.error(new Error('Whoops, something bad happened'));
// Prints: [Error: Whoops, something bad happened], to err

const name = 'Will Robinson';
myConsole.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to err

• @see source

Prints to stdout with newline. Multiple arguments can be passed, with the first used as the primary message and all additional used as substitution values similar to printf(3) (the arguments are all passed to util.format()).

const count = 5;
console.log('count: %d', count);
// Prints: count: 5, to stdout
console.log('count:', count);
// Prints: count: 5, to stdout

See util.format() for more information.

• @since v0.1.100

Allows manipulation and formatting of text strings and determination and location of substrings within strings.

Plugin to add support for parsing from HTML.

• @this processor.
• @param Configuration (optional).
• @returns Nothing.

Turn HTML into markdown.

Notes

• if a processor is given, runs the (remark) plugins used on it with an mdast tree, then discards the result (bridge mode)
• otherwise, returns an mdast tree, the plugins used after rehypeRemark are remark plugins (mutate mode)

👉 Note: It’s highly unlikely that you want to pass a processor.

• @overload
• @overload
• @param destination Processor or configuration (optional).
• @param options When a processor was given, configuration (optional).
• @returns Transform.

Add support for serializing to markdown.

• @this processor.
• @param Configuration (optional).
• @returns Nothing.

Create a new processor.

• @example This example shows how a new processor can be created (from remark) and linked to stdin(4) and stdout(4).

  import process from 'node:process'
  import concatStream from 'concat-stream'
  import {remark} from 'remark'
  
  process.stdin.pipe(
    concatStream(function (buf) {
      process.stdout.write(String(remark().processSync(buf)))
    })
  )
  

• @returns New unfrozen processor (processor). This processor is configured to work the same as its ancestor. When the descendant processor is configured in the future it does not affect the ancestral processor.

Create a new processor.

• @example This example shows how a new processor can be created (from remark) and linked to stdin(4) and stdout(4).

  import process from 'node:process'
  import concatStream from 'concat-stream'
  import {remark} from 'remark'
  
  process.stdin.pipe(
    concatStream(function (buf) {
      process.stdout.write(String(remark().processSync(buf)))
    })
  )
  

• @returns New unfrozen processor (processor). This processor is configured to work the same as its ancestor. When the descendant processor is configured in the future it does not affect the ancestral processor.

Configure the processor to use a plugin, a list of usable values, or a preset.

If the processor is already using a plugin, the previous plugin configuration is changed based on the options that are passed in. In other words, the plugin is not added a second time.

Note: use cannot be called on frozen processors. Call the processor first to create a new unfrozen processor.

• @example There are many ways to pass plugins to .use(). This example gives an overview:

  import {unified} from 'unified'
  
  unified()
    // Plugin with options:
    .use(pluginA, {x: true, y: true})
    // Passing the same plugin again merges configuration (to `{x: true, y: false, z: true}`):
    .use(pluginA, {y: false, z: true})
    // Plugins:
    .use([pluginB, pluginC])
    // Two plugins, the second with options:
    .use([pluginD, [pluginE, {}]])
    // Preset with plugins and settings:
    .use({plugins: [pluginF, [pluginG, {}]], settings: {position: false}})
    // Settings only:
    .use({settings: {position: false}})
  

• @template {Array} [Parameters=[]]
• @template {Node | string | undefined} [Input=undefined]
• @template [Output=Input]
• @overload
• @overload
• @overload
• @param value Usable value.
• @param parameters Parameters, when a plugin is given as a usable value.
• @returns Current processor.

Plugin to add support for parsing from HTML.

• @this processor.
• @param Configuration (optional).
• @returns Nothing.

Configure the processor to use a plugin, a list of usable values, or a preset.

If the processor is already using a plugin, the previous plugin configuration is changed based on the options that are passed in. In other words, the plugin is not added a second time.

Note: use cannot be called on frozen processors. Call the processor first to create a new unfrozen processor.

• @example There are many ways to pass plugins to .use(). This example gives an overview:

  import {unified} from 'unified'
  
  unified()
    // Plugin with options:
    .use(pluginA, {x: true, y: true})
    // Passing the same plugin again merges configuration (to `{x: true, y: false, z: true}`):
    .use(pluginA, {y: false, z: true})
    // Plugins:
    .use([pluginB, pluginC])
    // Two plugins, the second with options:
    .use([pluginD, [pluginE, {}]])
    // Preset with plugins and settings:
    .use({plugins: [pluginF, [pluginG, {}]], settings: {position: false}})
    // Settings only:
    .use({settings: {position: false}})
  

• @template {Array} [Parameters=[]]
• @template {Node | string | undefined} [Input=undefined]
• @template [Output=Input]
• @overload
• @overload
• @overload
• @param value Usable value.
• @param parameters Parameters, when a plugin is given as a usable value.
• @returns Current processor.

Turn HTML into markdown.

Notes

• if a processor is given, runs the (remark) plugins used on it with an mdast tree, then discards the result (bridge mode)
• otherwise, returns an mdast tree, the plugins used after rehypeRemark are remark plugins (mutate mode)

👉 Note: It’s highly unlikely that you want to pass a processor.

• @overload
• @overload
• @param destination Processor or configuration (optional).
• @param options When a processor was given, configuration (optional).
• @returns Transform.

Configure the processor to use a plugin, a list of usable values, or a preset.

If the processor is already using a plugin, the previous plugin configuration is changed based on the options that are passed in. In other words, the plugin is not added a second time.

Note: use cannot be called on frozen processors. Call the processor first to create a new unfrozen processor.

• @example There are many ways to pass plugins to .use(). This example gives an overview:

  import {unified} from 'unified'
  
  unified()
    // Plugin with options:
    .use(pluginA, {x: true, y: true})
    // Passing the same plugin again merges configuration (to `{x: true, y: false, z: true}`):
    .use(pluginA, {y: false, z: true})
    // Plugins:
    .use([pluginB, pluginC])
    // Two plugins, the second with options:
    .use([pluginD, [pluginE, {}]])
    // Preset with plugins and settings:
    .use({plugins: [pluginF, [pluginG, {}]], settings: {position: false}})
    // Settings only:
    .use({settings: {position: false}})
  

• @template {Array} [Parameters=[]]
• @template {Node | string | undefined} [Input=undefined]
• @template [Output=Input]
• @overload
• @overload
• @overload
• @param value Usable value.
• @param parameters Parameters, when a plugin is given as a usable value.
• @returns Current processor.

Add support for serializing to markdown.

• @this processor.
• @param Configuration (optional).
• @returns Nothing.

Process the given file as configured on the processor.

Note: process freezes the processor if not already frozen.

Note: process performs the parse, run, and stringify phases.

• @overload
• @overload
• @param file File (optional); typically string or VFile]; any value accepted as x in new VFile(x).
• @param done Callback (optional).
• @returns Nothing if done is given. Otherwise a promise, rejected with a fatal error or resolved with the processed file. The parsed, transformed, and compiled value is available at file.value (see note).

  Note: unified typically compiles by serializing: most compilers return string (or Uint8Array). Some compilers, such as the one configured with rehype-react, return other values (in this case, a React tree). If you’re using a compiler that doesn’t serialize, expect different result values.

  To register custom results in TypeScript, add them to {@linkcode CompileResultMap}.

The console module provides a simple debugging console that is similar to the JavaScript console mechanism provided by web browsers.

The module exports two specific components:

• A Console class with methods such as console.log(), console.error() and console.warn() that can be used to write to any Node.js stream.
• A global console instance configured to write to process.stdout and process.stderr. The global console can be used without importing the node:console module.

Warning: The global console object's methods are neither consistently synchronous like the browser APIs they resemble, nor are they consistently asynchronous like all other Node.js streams. See the note on process I/O for more information.

Example using the global console:

console.log('hello world');
// Prints: hello world, to stdout
console.log('hello %s', 'world');
// Prints: hello world, to stdout
console.error(new Error('Whoops, something bad happened'));
// Prints error message and stack trace to stderr:
//   Error: Whoops, something bad happened
//     at [eval]:5:15
//     at Script.runInThisContext (node:vm:132:18)
//     at Object.runInThisContext (node:vm:309:38)
//     at node:internal/process/execution:77:19
//     at [eval]-wrapper:6:22
//     at evalScript (node:internal/process/execution:76:60)
//     at node:internal/main/eval_string:23:3

const name = 'Will Robinson';
console.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to stderr

Example using the Console class:

const out = getStreamSomehow();
const err = getStreamSomehow();
const myConsole = new console.Console(out, err);

myConsole.log('hello world');
// Prints: hello world, to out
myConsole.log('hello %s', 'world');
// Prints: hello world, to out
myConsole.error(new Error('Whoops, something bad happened'));
// Prints: [Error: Whoops, something bad happened], to err

const name = 'Will Robinson';
myConsole.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to err

• @see source

Prints to stdout with newline. Multiple arguments can be passed, with the first used as the primary message and all additional used as substitution values similar to printf(3) (the arguments are all passed to util.format()).

const count = 5;
console.log('count: %d', count);
// Prints: count: 5, to stdout
console.log('count:', count);
// Prints: count: 5, to stdout

See util.format() for more information.

• @since v0.1.100

Allows manipulation and formatting of text strings and determination and location of substrings within strings.

Plugin to add support for serializing as HTML.

• @this processor.
• @param Configuration (optional).
• @returns Nothing.

Add support for parsing from markdown.

• @this processor.
• @param Configuration (optional).
• @returns Nothing.

Turn markdown into HTML.

Notes

Signature

• if a processor is given, runs the (rehype) plugins used on it with a hast tree, then discards the result (bridge mode)
• otherwise, returns a hast tree, the plugins used after remarkRehype are rehype plugins (mutate mode)

👉 Note: It’s highly unlikely that you want to pass a processor.

HTML

Raw HTML is available in mdast as html nodes and can be embedded in hast as semistandard raw nodes. Most plugins ignore raw nodes but two notable ones don’t:

• rehype-stringify also has an option allowDangerousHtml which will output the raw HTML. This is typically discouraged as noted by the option name but is useful if you completely trust authors
• rehype-raw can handle the raw embedded HTML strings by parsing them into standard hast nodes (element, text, etc). This is a heavy task as it needs a full HTML parser, but it is the only way to support untrusted content

Footnotes

Many options supported here relate to footnotes. Footnotes are not specified by CommonMark, which we follow by default. They are supported by GitHub, so footnotes can be enabled in markdown with remark-gfm.

The options footnoteBackLabel and footnoteLabel define natural language that explains footnotes, which is hidden for sighted users but shown to assistive technology. When your page is not in English, you must define translated values.

Back references use ARIA attributes, but the section label itself uses a heading that is hidden with an sr-only class. To show it to sighted users, define different attributes in footnoteLabelProperties.

Clobbering

Footnotes introduces a problem, as it links footnote calls to footnote definitions on the page through id attributes generated from user content, which results in DOM clobbering.

DOM clobbering is this:

<p id=x></p>
<script>alert(x) // `x` now refers to the DOM `p#x` element</script>

Elements by their ID are made available by browsers on the window object, which is a security risk. Using a prefix solves this problem.

More information on how to handle clobbering and the prefix is explained in Example: headings (DOM clobbering) in rehype-sanitize.

Unknown nodes

Unknown nodes are nodes with a type that isn’t in handlers or passThrough. The default behavior for unknown nodes is:

• when the node has a value (and doesn’t have data.hName, data.hProperties, or data.hChildren, see later), create a hast text node
• otherwise, create a <div> element (which could be changed with data.hName), with its children mapped from mdast to hast as well

This behavior can be changed by passing an unknownHandler.

• @overload
• @overload
• @param destination Processor or configuration (optional).
• @param options When a processor was given, configuration (optional).
• @returns Transform.

Create a new processor.

• @example This example shows how a new processor can be created (from remark) and linked to stdin(4) and stdout(4).

  import process from 'node:process'
  import concatStream from 'concat-stream'
  import {remark} from 'remark'
  
  process.stdin.pipe(
    concatStream(function (buf) {
      process.stdout.write(String(remark().processSync(buf)))
    })
  )
  

• @returns New unfrozen processor (processor). This processor is configured to work the same as its ancestor. When the descendant processor is configured in the future it does not affect the ancestral processor.

Create a new processor.

• @example This example shows how a new processor can be created (from remark) and linked to stdin(4) and stdout(4).

  import process from 'node:process'
  import concatStream from 'concat-stream'
  import {remark} from 'remark'
  
  process.stdin.pipe(
    concatStream(function (buf) {
      process.stdout.write(String(remark().processSync(buf)))
    })
  )
  

• @returns New unfrozen processor (processor). This processor is configured to work the same as its ancestor. When the descendant processor is configured in the future it does not affect the ancestral processor.

Configure the processor to use a plugin, a list of usable values, or a preset.

If the processor is already using a plugin, the previous plugin configuration is changed based on the options that are passed in. In other words, the plugin is not added a second time.

Note: use cannot be called on frozen processors. Call the processor first to create a new unfrozen processor.

• @example There are many ways to pass plugins to .use(). This example gives an overview:

  import {unified} from 'unified'
  
  unified()
    // Plugin with options:
    .use(pluginA, {x: true, y: true})
    // Passing the same plugin again merges configuration (to `{x: true, y: false, z: true}`):
    .use(pluginA, {y: false, z: true})
    // Plugins:
    .use([pluginB, pluginC])
    // Two plugins, the second with options:
    .use([pluginD, [pluginE, {}]])
    // Preset with plugins and settings:
    .use({plugins: [pluginF, [pluginG, {}]], settings: {position: false}})
    // Settings only:
    .use({settings: {position: false}})
  

• @template {Array} [Parameters=[]]
• @template {Node | string | undefined} [Input=undefined]
• @template [Output=Input]
• @overload
• @overload
• @overload
• @param value Usable value.
• @param parameters Parameters, when a plugin is given as a usable value.
• @returns Current processor.

Add support for parsing from markdown.

• @this processor.
• @param Configuration (optional).
• @returns Nothing.

Configure the processor to use a plugin, a list of usable values, or a preset.

If the processor is already using a plugin, the previous plugin configuration is changed based on the options that are passed in. In other words, the plugin is not added a second time.

Note: use cannot be called on frozen processors. Call the processor first to create a new unfrozen processor.

• @example There are many ways to pass plugins to .use(). This example gives an overview:

  import {unified} from 'unified'
  
  unified()
    // Plugin with options:
    .use(pluginA, {x: true, y: true})
    // Passing the same plugin again merges configuration (to `{x: true, y: false, z: true}`):
    .use(pluginA, {y: false, z: true})
    // Plugins:
    .use([pluginB, pluginC])
    // Two plugins, the second with options:
    .use([pluginD, [pluginE, {}]])
    // Preset with plugins and settings:
    .use({plugins: [pluginF, [pluginG, {}]], settings: {position: false}})
    // Settings only:
    .use({settings: {position: false}})
  

• @template {Array} [Parameters=[]]
• @template {Node | string | undefined} [Input=undefined]
• @template [Output=Input]
• @overload
• @overload
• @overload
• @param value Usable value.
• @param parameters Parameters, when a plugin is given as a usable value.
• @returns Current processor.

Turn markdown into HTML.

Notes

Signature

• if a processor is given, runs the (rehype) plugins used on it with a hast tree, then discards the result (bridge mode)
• otherwise, returns a hast tree, the plugins used after remarkRehype are rehype plugins (mutate mode)

👉 Note: It’s highly unlikely that you want to pass a processor.

HTML

Raw HTML is available in mdast as html nodes and can be embedded in hast as semistandard raw nodes. Most plugins ignore raw nodes but two notable ones don’t:

• rehype-stringify also has an option allowDangerousHtml which will output the raw HTML. This is typically discouraged as noted by the option name but is useful if you completely trust authors
• rehype-raw can handle the raw embedded HTML strings by parsing them into standard hast nodes (element, text, etc). This is a heavy task as it needs a full HTML parser, but it is the only way to support untrusted content

Footnotes

Many options supported here relate to footnotes. Footnotes are not specified by CommonMark, which we follow by default. They are supported by GitHub, so footnotes can be enabled in markdown with remark-gfm.

The options footnoteBackLabel and footnoteLabel define natural language that explains footnotes, which is hidden for sighted users but shown to assistive technology. When your page is not in English, you must define translated values.

Back references use ARIA attributes, but the section label itself uses a heading that is hidden with an sr-only class. To show it to sighted users, define different attributes in footnoteLabelProperties.

Clobbering

Footnotes introduces a problem, as it links footnote calls to footnote definitions on the page through id attributes generated from user content, which results in DOM clobbering.

DOM clobbering is this:

<p id=x></p>
<script>alert(x) // `x` now refers to the DOM `p#x` element</script>

Elements by their ID are made available by browsers on the window object, which is a security risk. Using a prefix solves this problem.

More information on how to handle clobbering and the prefix is explained in Example: headings (DOM clobbering) in rehype-sanitize.

Unknown nodes

Unknown nodes are nodes with a type that isn’t in handlers or passThrough. The default behavior for unknown nodes is:

• when the node has a value (and doesn’t have data.hName, data.hProperties, or data.hChildren, see later), create a hast text node
• otherwise, create a <div> element (which could be changed with data.hName), with its children mapped from mdast to hast as well

This behavior can be changed by passing an unknownHandler.

• @overload
• @overload
• @param destination Processor or configuration (optional).
• @param options When a processor was given, configuration (optional).
• @returns Transform.

Configure the processor to use a plugin, a list of usable values, or a preset.

If the processor is already using a plugin, the previous plugin configuration is changed based on the options that are passed in. In other words, the plugin is not added a second time.

Note: use cannot be called on frozen processors. Call the processor first to create a new unfrozen processor.

• @example There are many ways to pass plugins to .use(). This example gives an overview:

  import {unified} from 'unified'
  
  unified()
    // Plugin with options:
    .use(pluginA, {x: true, y: true})
    // Passing the same plugin again merges configuration (to `{x: true, y: false, z: true}`):
    .use(pluginA, {y: false, z: true})
    // Plugins:
    .use([pluginB, pluginC])
    // Two plugins, the second with options:
    .use([pluginD, [pluginE, {}]])
    // Preset with plugins and settings:
    .use({plugins: [pluginF, [pluginG, {}]], settings: {position: false}})
    // Settings only:
    .use({settings: {position: false}})
  

• @template {Array} [Parameters=[]]
• @template {Node | string | undefined} [Input=undefined]
• @template [Output=Input]
• @overload
• @overload
• @overload
• @param value Usable value.
• @param parameters Parameters, when a plugin is given as a usable value.
• @returns Current processor.

Plugin to add support for serializing as HTML.

• @this processor.
• @param Configuration (optional).
• @returns Nothing.

Process the given file as configured on the processor.

Note: process freezes the processor if not already frozen.

Note: process performs the parse, run, and stringify phases.

• @overload
• @overload
• @param file File (optional); typically string or VFile]; any value accepted as x in new VFile(x).
• @param done Callback (optional).
• @returns Nothing if done is given. Otherwise a promise, rejected with a fatal error or resolved with the processed file. The parsed, transformed, and compiled value is available at file.value (see note).

  Note: unified typically compiles by serializing: most compilers return string (or Uint8Array). Some compilers, such as the one configured with rehype-react, return other values (in this case, a React tree). If you’re using a compiler that doesn’t serialize, expect different result values.

  To register custom results in TypeScript, add them to {@linkcode CompileResultMap}.

The console module provides a simple debugging console that is similar to the JavaScript console mechanism provided by web browsers.

The module exports two specific components:

• A Console class with methods such as console.log(), console.error() and console.warn() that can be used to write to any Node.js stream.
• A global console instance configured to write to process.stdout and process.stderr. The global console can be used without importing the node:console module.

Warning: The global console object's methods are neither consistently synchronous like the browser APIs they resemble, nor are they consistently asynchronous like all other Node.js streams. See the note on process I/O for more information.

Example using the global console:

console.log('hello world');
// Prints: hello world, to stdout
console.log('hello %s', 'world');
// Prints: hello world, to stdout
console.error(new Error('Whoops, something bad happened'));
// Prints error message and stack trace to stderr:
//   Error: Whoops, something bad happened
//     at [eval]:5:15
//     at Script.runInThisContext (node:vm:132:18)
//     at Object.runInThisContext (node:vm:309:38)
//     at node:internal/process/execution:77:19
//     at [eval]-wrapper:6:22
//     at evalScript (node:internal/process/execution:76:60)
//     at node:internal/main/eval_string:23:3

const name = 'Will Robinson';
console.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to stderr

Example using the Console class:

const out = getStreamSomehow();
const err = getStreamSomehow();
const myConsole = new console.Console(out, err);

myConsole.log('hello world');
// Prints: hello world, to out
myConsole.log('hello %s', 'world');
// Prints: hello world, to out
myConsole.error(new Error('Whoops, something bad happened'));
// Prints: [Error: Whoops, something bad happened], to err

const name = 'Will Robinson';
myConsole.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to err

• @see source

Prints to stdout with newline. Multiple arguments can be passed, with the first used as the primary message and all additional used as substitution values similar to printf(3) (the arguments are all passed to util.format()).

const count = 5;
console.log('count: %d', count);
// Prints: count: 5, to stdout
console.log('count:', count);
// Prints: count: 5, to stdout

See util.format() for more information.

• @since v0.1.100

Allows manipulation and formatting of text strings and determination and location of substrings within strings.

Parse the tree (and raw nodes) again, keeping positional info okay.

• @param options Configuration (optional).
• @returns Transform.

Plugin to add support for serializing as HTML.

• @this processor.
• @param Configuration (optional).
• @returns Nothing.

Add support for parsing from markdown.

• @this processor.
• @param Configuration (optional).
• @returns Nothing.

Turn markdown into HTML.

Notes

Signature

• if a processor is given, runs the (rehype) plugins used on it with a hast tree, then discards the result (bridge mode)
• otherwise, returns a hast tree, the plugins used after remarkRehype are rehype plugins (mutate mode)

👉 Note: It’s highly unlikely that you want to pass a processor.

HTML

Raw HTML is available in mdast as html nodes and can be embedded in hast as semistandard raw nodes. Most plugins ignore raw nodes but two notable ones don’t:

• rehype-stringify also has an option allowDangerousHtml which will output the raw HTML. This is typically discouraged as noted by the option name but is useful if you completely trust authors
• rehype-raw can handle the raw embedded HTML strings by parsing them into standard hast nodes (element, text, etc). This is a heavy task as it needs a full HTML parser, but it is the only way to support untrusted content

Footnotes

Many options supported here relate to footnotes. Footnotes are not specified by CommonMark, which we follow by default. They are supported by GitHub, so footnotes can be enabled in markdown with remark-gfm.

The options footnoteBackLabel and footnoteLabel define natural language that explains footnotes, which is hidden for sighted users but shown to assistive technology. When your page is not in English, you must define translated values.

Back references use ARIA attributes, but the section label itself uses a heading that is hidden with an sr-only class. To show it to sighted users, define different attributes in footnoteLabelProperties.

Clobbering

Footnotes introduces a problem, as it links footnote calls to footnote definitions on the page through id attributes generated from user content, which results in DOM clobbering.

DOM clobbering is this:

<p id=x></p>
<script>alert(x) // `x` now refers to the DOM `p#x` element</script>

Elements by their ID are made available by browsers on the window object, which is a security risk. Using a prefix solves this problem.

More information on how to handle clobbering and the prefix is explained in Example: headings (DOM clobbering) in rehype-sanitize.

Unknown nodes

Unknown nodes are nodes with a type that isn’t in handlers or passThrough. The default behavior for unknown nodes is:

• when the node has a value (and doesn’t have data.hName, data.hProperties, or data.hChildren, see later), create a hast text node
• otherwise, create a <div> element (which could be changed with data.hName), with its children mapped from mdast to hast as well

This behavior can be changed by passing an unknownHandler.

• @overload
• @overload
• @param destination Processor or configuration (optional).
• @param options When a processor was given, configuration (optional).
• @returns Transform.

Create a new processor.

• @example This example shows how a new processor can be created (from remark) and linked to stdin(4) and stdout(4).

  import process from 'node:process'
  import concatStream from 'concat-stream'
  import {remark} from 'remark'
  
  process.stdin.pipe(
    concatStream(function (buf) {
      process.stdout.write(String(remark().processSync(buf)))
    })
  )
  

• @returns New unfrozen processor (processor). This processor is configured to work the same as its ancestor. When the descendant processor is configured in the future it does not affect the ancestral processor.

Create a new processor.

• @example This example shows how a new processor can be created (from remark) and linked to stdin(4) and stdout(4).

  import process from 'node:process'
  import concatStream from 'concat-stream'
  import {remark} from 'remark'
  
  process.stdin.pipe(
    concatStream(function (buf) {
      process.stdout.write(String(remark().processSync(buf)))
    })
  )
  

• @returns New unfrozen processor (processor). This processor is configured to work the same as its ancestor. When the descendant processor is configured in the future it does not affect the ancestral processor.

Configure the processor to use a plugin, a list of usable values, or a preset.

If the processor is already using a plugin, the previous plugin configuration is changed based on the options that are passed in. In other words, the plugin is not added a second time.

Note: use cannot be called on frozen processors. Call the processor first to create a new unfrozen processor.

• @example There are many ways to pass plugins to .use(). This example gives an overview:

  import {unified} from 'unified'
  
  unified()
    // Plugin with options:
    .use(pluginA, {x: true, y: true})
    // Passing the same plugin again merges configuration (to `{x: true, y: false, z: true}`):
    .use(pluginA, {y: false, z: true})
    // Plugins:
    .use([pluginB, pluginC])
    // Two plugins, the second with options:
    .use([pluginD, [pluginE, {}]])
    // Preset with plugins and settings:
    .use({plugins: [pluginF, [pluginG, {}]], settings: {position: false}})
    // Settings only:
    .use({settings: {position: false}})
  

• @template {Array} [Parameters=[]]
• @template {Node | string | undefined} [Input=undefined]
• @template [Output=Input]
• @overload
• @overload
• @overload
• @param value Usable value.
• @param parameters Parameters, when a plugin is given as a usable value.
• @returns Current processor.

Add support for parsing from markdown.

• @this processor.
• @param Configuration (optional).
• @returns Nothing.

Configure the processor to use a plugin, a list of usable values, or a preset.

If the processor is already using a plugin, the previous plugin configuration is changed based on the options that are passed in. In other words, the plugin is not added a second time.

Note: use cannot be called on frozen processors. Call the processor first to create a new unfrozen processor.

• @example There are many ways to pass plugins to .use(). This example gives an overview:

  import {unified} from 'unified'
  
  unified()
    // Plugin with options:
    .use(pluginA, {x: true, y: true})
    // Passing the same plugin again merges configuration (to `{x: true, y: false, z: true}`):
    .use(pluginA, {y: false, z: true})
    // Plugins:
    .use([pluginB, pluginC])
    // Two plugins, the second with options:
    .use([pluginD, [pluginE, {}]])
    // Preset with plugins and settings:
    .use({plugins: [pluginF, [pluginG, {}]], settings: {position: false}})
    // Settings only:
    .use({settings: {position: false}})
  

• @template {Array} [Parameters=[]]
• @template {Node | string | undefined} [Input=undefined]
• @template [Output=Input]
• @overload
• @overload
• @overload
• @param value Usable value.
• @param parameters Parameters, when a plugin is given as a usable value.
• @returns Current processor.

Turn markdown into HTML.

Notes

Signature

• if a processor is given, runs the (rehype) plugins used on it with a hast tree, then discards the result (bridge mode)
• otherwise, returns a hast tree, the plugins used after remarkRehype are rehype plugins (mutate mode)

👉 Note: It’s highly unlikely that you want to pass a processor.

HTML

Raw HTML is available in mdast as html nodes and can be embedded in hast as semistandard raw nodes. Most plugins ignore raw nodes but two notable ones don’t:

• rehype-stringify also has an option allowDangerousHtml which will output the raw HTML. This is typically discouraged as noted by the option name but is useful if you completely trust authors
• rehype-raw can handle the raw embedded HTML strings by parsing them into standard hast nodes (element, text, etc). This is a heavy task as it needs a full HTML parser, but it is the only way to support untrusted content

Footnotes

Many options supported here relate to footnotes. Footnotes are not specified by CommonMark, which we follow by default. They are supported by GitHub, so footnotes can be enabled in markdown with remark-gfm.

The options footnoteBackLabel and footnoteLabel define natural language that explains footnotes, which is hidden for sighted users but shown to assistive technology. When your page is not in English, you must define translated values.

Back references use ARIA attributes, but the section label itself uses a heading that is hidden with an sr-only class. To show it to sighted users, define different attributes in footnoteLabelProperties.

Clobbering

Footnotes introduces a problem, as it links footnote calls to footnote definitions on the page through id attributes generated from user content, which results in DOM clobbering.

DOM clobbering is this:

<p id=x></p>
<script>alert(x) // `x` now refers to the DOM `p#x` element</script>

Elements by their ID are made available by browsers on the window object, which is a security risk. Using a prefix solves this problem.

More information on how to handle clobbering and the prefix is explained in Example: headings (DOM clobbering) in rehype-sanitize.

Unknown nodes

Unknown nodes are nodes with a type that isn’t in handlers or passThrough. The default behavior for unknown nodes is:

• when the node has a value (and doesn’t have data.hName, data.hProperties, or data.hChildren, see later), create a hast text node
• otherwise, create a <div> element (which could be changed with data.hName), with its children mapped from mdast to hast as well

This behavior can be changed by passing an unknownHandler.

• @overload
• @overload
• @param destination Processor or configuration (optional).
• @param options When a processor was given, configuration (optional).
• @returns Transform.

Configure the processor to use a plugin, a list of usable values, or a preset.

If the processor is already using a plugin, the previous plugin configuration is changed based on the options that are passed in. In other words, the plugin is not added a second time.

Note: use cannot be called on frozen processors. Call the processor first to create a new unfrozen processor.

• @example There are many ways to pass plugins to .use(). This example gives an overview:

  import {unified} from 'unified'
  
  unified()
    // Plugin with options:
    .use(pluginA, {x: true, y: true})
    // Passing the same plugin again merges configuration (to `{x: true, y: false, z: true}`):
    .use(pluginA, {y: false, z: true})
    // Plugins:
    .use([pluginB, pluginC])
    // Two plugins, the second with options:
    .use([pluginD, [pluginE, {}]])
    // Preset with plugins and settings:
    .use({plugins: [pluginF, [pluginG, {}]], settings: {position: false}})
    // Settings only:
    .use({settings: {position: false}})
  

• @template {Array} [Parameters=[]]
• @template {Node | string | undefined} [Input=undefined]
• @template [Output=Input]
• @overload
• @overload
• @overload
• @param value Usable value.
• @param parameters Parameters, when a plugin is given as a usable value.
• @returns Current processor.

Parse the tree (and raw nodes) again, keeping positional info okay.

• @param options Configuration (optional).
• @returns Transform.

Configure the processor to use a plugin, a list of usable values, or a preset.

If the processor is already using a plugin, the previous plugin configuration is changed based on the options that are passed in. In other words, the plugin is not added a second time.

Note: use cannot be called on frozen processors. Call the processor first to create a new unfrozen processor.

• @example There are many ways to pass plugins to .use(). This example gives an overview:

  import {unified} from 'unified'
  
  unified()
    // Plugin with options:
    .use(pluginA, {x: true, y: true})
    // Passing the same plugin again merges configuration (to `{x: true, y: false, z: true}`):
    .use(pluginA, {y: false, z: true})
    // Plugins:
    .use([pluginB, pluginC])
    // Two plugins, the second with options:
    .use([pluginD, [pluginE, {}]])
    // Preset with plugins and settings:
    .use({plugins: [pluginF, [pluginG, {}]], settings: {position: false}})
    // Settings only:
    .use({settings: {position: false}})
  

• @template {Array} [Parameters=[]]
• @template {Node | string | undefined} [Input=undefined]
• @template [Output=Input]
• @overload
• @overload
• @overload
• @param value Usable value.
• @param parameters Parameters, when a plugin is given as a usable value.
• @returns Current processor.

Plugin to add support for serializing as HTML.

• @this processor.
• @param Configuration (optional).
• @returns Nothing.

Process the given file as configured on the processor.

Note: process freezes the processor if not already frozen.

Note: process performs the parse, run, and stringify phases.

• @overload
• @overload
• @param file File (optional); typically string or VFile]; any value accepted as x in new VFile(x).
• @param done Callback (optional).
• @returns Nothing if done is given. Otherwise a promise, rejected with a fatal error or resolved with the processed file. The parsed, transformed, and compiled value is available at file.value (see note).

  Note: unified typically compiles by serializing: most compilers return string (or Uint8Array). Some compilers, such as the one configured with rehype-react, return other values (in this case, a React tree). If you’re using a compiler that doesn’t serialize, expect different result values.

  To register custom results in TypeScript, add them to {@linkcode CompileResultMap}.

The console module provides a simple debugging console that is similar to the JavaScript console mechanism provided by web browsers.

The module exports two specific components:

• A Console class with methods such as console.log(), console.error() and console.warn() that can be used to write to any Node.js stream.
• A global console instance configured to write to process.stdout and process.stderr. The global console can be used without importing the node:console module.

Warning: The global console object's methods are neither consistently synchronous like the browser APIs they resemble, nor are they consistently asynchronous like all other Node.js streams. See the note on process I/O for more information.

Example using the global console:

console.log('hello world');
// Prints: hello world, to stdout
console.log('hello %s', 'world');
// Prints: hello world, to stdout
console.error(new Error('Whoops, something bad happened'));
// Prints error message and stack trace to stderr:
//   Error: Whoops, something bad happened
//     at [eval]:5:15
//     at Script.runInThisContext (node:vm:132:18)
//     at Object.runInThisContext (node:vm:309:38)
//     at node:internal/process/execution:77:19
//     at [eval]-wrapper:6:22
//     at evalScript (node:internal/process/execution:76:60)
//     at node:internal/main/eval_string:23:3

const name = 'Will Robinson';
console.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to stderr

Example using the Console class:

const out = getStreamSomehow();
const err = getStreamSomehow();
const myConsole = new console.Console(out, err);

myConsole.log('hello world');
// Prints: hello world, to out
myConsole.log('hello %s', 'world');
// Prints: hello world, to out
myConsole.error(new Error('Whoops, something bad happened'));
// Prints: [Error: Whoops, something bad happened], to err

const name = 'Will Robinson';
myConsole.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to err

• @see source

Prints to stdout with newline. Multiple arguments can be passed, with the first used as the primary message and all additional used as substitution values similar to printf(3) (the arguments are all passed to util.format()).

const count = 5;
console.log('count: %d', count);
// Prints: count: 5, to stdout
console.log('count:', count);
// Prints: count: 5, to stdout

See util.format() for more information.

• @since v0.1.100

Allows manipulation and formatting of text strings and determination and location of substrings within strings.