# remark-parse
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[Parser][] for [**unified**][unified].
Parses Markdown to [**mdast**][mdast] syntax trees.
Used in the [**remark** processor][remark] but can be used on its own as well.
Can be [extended][extend] to change how markdown is parsed.
## Sponsors
[**Read more about the unified collective on Medium Β»**][announcement]
## Install
[npm][]:
```sh
npm install remark-parse
```
## Use
```js
var unified = require('unified')
var createStream = require('unified-stream')
var markdown = require('remark-parse')
var remark2rehype = require('remark-rehype')
var html = require('rehype-stringify')
var processor = unified()
.use(markdown, {commonmark: true})
.use(remark2rehype)
.use(html)
process.stdin.pipe(createStream(processor)).pipe(process.stdout)
```
[See **unified** for more examples Β»][unified]
## Table of Contents
* [API](#api)
* [`processor().use(parse[, options])`](#processoruseparse-options)
* [`parse.Parser`](#parseparser)
* [Extending the Parser](#extending-the-parser)
* [`Parser#blockTokenizers`](#parserblocktokenizers)
* [`Parser#blockMethods`](#parserblockmethods)
* [`Parser#inlineTokenizers`](#parserinlinetokenizers)
* [`Parser#inlineMethods`](#parserinlinemethods)
* [`function tokenizer(eat, value, silent)`](#function-tokenizereat-value-silent)
* [`tokenizer.locator(value, fromIndex)`](#tokenizerlocatorvalue-fromindex)
* [`eat(subvalue)`](#eatsubvalue)
* [`add(node[, parent])`](#addnode-parent)
* [`add.test()`](#addtest)
* [`add.reset(node[, parent])`](#addresetnode-parent)
* [Turning off a tokenizer](#turning-off-a-tokenizer)
* [Security](#security)
* [Contribute](#contribute)
* [License](#license)
## API
[See **unified** for API docs Β»][unified]
### `processor().use(parse[, options])`
Configure the `processor` to read Markdown as input and process
[**mdast**][mdast] syntax trees.
##### `options`
Options can be passed directly, or passed later through
[`processor.data()`][data].
###### `options.gfm`
GFM mode (`boolean`, default: `true`).
```markdown
hello ~~hi~~ world
```
Turns on:
* [Fenced code blocks](https://help.github.com/articles/creating-and-highlighting-code-blocks#fenced-code-blocks)
* [Autolinking of URLs](https://help.github.com/articles/autolinked-references-and-urls)
* [Deletions (strikethrough)](https://help.github.com/articles/basic-writing-and-formatting-syntax#styling-text)
* [Task lists](https://help.github.com/articles/basic-writing-and-formatting-syntax#task-lists)
* [Tables](https://help.github.com/articles/organizing-information-with-tables)
###### `options.commonmark`
CommonMark mode (`boolean`, default: `false`).
```markdown
This is a paragraph
and this is also part of the preceding paragraph.
```
Allows:
* Empty lines to split blockquotes
* Parentheses (`(` and `)`) around link and image titles
* Any escaped [ASCII punctuation][escapes] character
* Closing parenthesis (`)`) as an ordered list marker
* URL definitions (and footnotes, when enabled) in blockquotes
Disallows:
* Indented code blocks directly following a paragraph
* ATX headings (`# Hash headings`) without spacing after opening hashes or and
before closing hashes
* Setext headings (`Underline headings\n---`) when following a paragraph
* Newlines in link and image titles
* White space in link and image URLs in auto-links (links in brackets, `<` and
`>`)
* Lazy blockquote continuation, lines not preceded by a greater than character
(`>`), for lists, code, and thematic breaks
###### `options.footnotes`
Footnotes mode (`boolean`, default: `false`).
```markdown
Something something[^or something?].
And something else[^1].
[^1]: This reference footnote contains a paragraph...
* ...and a list
```
Enables reference footnotes and inline footnotes.
Both are wrapped in square brackets and preceded by a caret (`^`), and can be
referenced from inside other footnotes.
###### `options.pedantic`
Pedantic mode (`boolean`, default: `false`).
```markdown
Check out some_file_name.txt
```
Turns on:
* Emphasis (`_alpha_`) and importance (`__bravo__`) with underscores in words
* Unordered lists with different markers (`*`, `-`, `+`)
* If `commonmark` is also turned on, ordered lists with different markers
(`.`, `)`)
* And removes less spaces in list items (at most four, instead of the whole
indent)
###### `options.blocks`
Blocks (`Array.`, default: list of [block HTML elements][blocks]).
```markdown
foo
```
Defines which HTML elements are seen as block level.
### `parse.Parser`
Access to the [parser][], if you need it.
## Extending the Parser
Typically, using [*transformers*][transformer] to manipulate a syntax tree
produces the desired output.
Sometimes, such as when introducing new syntactic entities with a certain
precedence, interfacing with the parser is necessary.
If the `remark-parse` plugin is used, it adds a [`Parser`][parser] constructor
function to the `processor`.
Other plugins can add tokenizers to its prototype to change how Markdown is
parsed.
The below plugin adds a [tokenizer][] for at-mentions.
```js
module.exports = mentions
function mentions() {
var Parser = this.Parser
var tokenizers = Parser.prototype.inlineTokenizers
var methods = Parser.prototype.inlineMethods
// Add an inline tokenizer (defined in the following example).
tokenizers.mention = tokenizeMention
// Run it just before `text`.
methods.splice(methods.indexOf('text'), 0, 'mention')
}
```
### `Parser#blockTokenizers`
Map of names to [tokenizer][]s (`Object.`).
These tokenizers (such as `fencedCode`, `table`, and `paragraph`) eat from the
start of a value to a line ending.
See `#blockMethods` below for a list of methods that are included by default.
### `Parser#blockMethods`
List of `blockTokenizers` names (`Array.`).
Specifies the order in which tokenizers run.
Precedence of default block methods is as follows:
* `newline`
* `indentedCode`
* `fencedCode`
* `blockquote`
* `atxHeading`
* `thematicBreak`
* `list`
* `setextHeading`
* `html`
* `footnote`
* `definition`
* `table`
* `paragraph`
### `Parser#inlineTokenizers`
Map of names to [tokenizer][]s (`Object.`).
These tokenizers (such as `url`, `reference`, and `emphasis`) eat from the start
of a value.
To increase performance, they depend on [locator][]s.
See `#inlineMethods` below for a list of methods that are included by default.
### `Parser#inlineMethods`
List of `inlineTokenizers` names (`Array.`).
Specifies the order in which tokenizers run.
Precedence of default inline methods is as follows:
* `escape`
* `autoLink`
* `url`
* `html`
* `link`
* `reference`
* `strong`
* `emphasis`
* `deletion`
* `code`
* `break`
* `text`
### `function tokenizer(eat, value, silent)`
There are two types of tokenizers: block level and inline level.
Both are functions, and work the same, but inline tokenizers must have a
[locator][].
The following example shows an inline tokenizer that is added by the mentions
plugin above.
```js
tokenizeMention.notInLink = true
tokenizeMention.locator = locateMention
function tokenizeMention(eat, value, silent) {
var match = /^@(\w+)/.exec(value)
if (match) {
if (silent) {
return true
}
return eat(match[0])({
type: 'link',
url: 'https://social-network/' + match[1],
children: [{type: 'text', value: match[0]}]
})
}
}
```
Tokenizers *test* whether a document starts with a certain syntactic entity.
In *silent* mode, they return whether that test passes.
In *normal* mode, they consume that token, a process which is called βeatingβ.
Locators enable inline tokenizers to function faster by providing where the next
entity may occur.
###### Signatures
* `Node? = tokenizer(eat, value)`
* `boolean? = tokenizer(eat, value, silent)`
###### Parameters
* `eat` ([`Function`][eat]) β Eat, when applicable, an entity
* `value` (`string`) β Value which may start an entity
* `silent` (`boolean`, optional) β Whether to detect or consume
###### Properties
* `locator` ([`Function`][locator]) β Required for inline tokenizers
* `onlyAtStart` (`boolean`) β Whether nodes can only be found at the beginning
of the document
* `notInBlock` (`boolean`) β Whether nodes cannot be in blockquotes, lists, or
footnote definitions
* `notInList` (`boolean`) β Whether nodes cannot be in lists
* `notInLink` (`boolean`) β Whether nodes cannot be in links
###### Returns
* `boolean?`, in *silent* mode β whether a node can be found at the start of
`value`
* [`Node?`][node], In *normal* mode β If it can be found at the start of
`value`
### `tokenizer.locator(value, fromIndex)`
Locators are required for inline tokenizers.
Their role is to keep parsing performant.
The following example shows a locator that is added by the mentions tokenizer
above.
```js
function locateMention(value, fromIndex) {
return value.indexOf('@', fromIndex)
}
```
Locators enable inline tokenizers to function faster by providing information on
where the next entity *may* occur.
Locators may be wrong, itβs OK if there actually isnβt a node to be found at the
index they return.
###### Parameters
* `value` (`string`) β Value which may contain an entity
* `fromIndex` (`number`) β Position to start searching at
###### Returns
`number` β Index at which an entity may start, and `-1` otherwise.
### `eat(subvalue)`
```js
var add = eat('foo')
```
Eat `subvalue`, which is a string at the start of the [tokenized][tokenizer]
`value`.
###### Parameters
* `subvalue` (`string`) - Value to eat
###### Returns
[`add`][add].
### `add(node[, parent])`
```js
var add = eat('foo')
add({type: 'text', value: 'foo'})
```
Add [positional information][position] to `node` and add `node` to `parent`.
###### Parameters
* `node` ([`Node`][node]) - Node to patch position on and to add
* `parent` ([`Parent`][parent], optional) - Place to add `node` to in the
syntax tree.
Defaults to the currently processed node
###### Returns
[`Node`][node] β The given `node`.
### `add.test()`
Get the [positional information][position] that would be patched on `node` by
`add`.
###### Returns
[`Position`][position].
### `add.reset(node[, parent])`
`add`, but resets the internal position.
Useful for example in lists, where the same content is first eaten for a list,
and later for list items.
###### Parameters
* `node` ([`Node`][node]) - Node to patch position on and insert
* `parent` ([`Node`][node], optional) - Place to add `node` to in
the syntax tree.
Defaults to the currently processed node
###### Returns
[`Node`][node] β The given node.
### Turning off a tokenizer
In some situations, you may want to turn off a tokenizer to avoid parsing that
syntactic feature.
Preferably, use the [`remark-disable-tokenizers`][remark-disable-tokenizers]
plugin to turn off tokenizers.
Alternatively, this can be done by replacing the tokenizer from
`blockTokenizers` (or `blockMethods`) or `inlineTokenizers` (or
`inlineMethods`).
The following example turns off indented code blocks:
```js
remarkParse.Parser.prototype.blockTokenizers.indentedCode = indentedCode
function indentedCode() {
return true
}
```
## Security
As Markdown is sometimes used for HTML, and improper use of HTML can open you up
to a [cross-site scripting (XSS)][xss] attack, use of remark can also be unsafe.
When going to HTML, use remark in combination with the [**rehype**][rehype]
ecosystem, and use [`rehype-sanitize`][sanitize] to make the tree safe.
Use of remark plugins could also open you up to other attacks.
Carefully assess each plugin and the risks involved in using them.
## Contribute
See [`contributing.md`][contributing] in [`remarkjs/.github`][health] for ways
to get started.
See [`support.md`][support] for ways to get help.
Ideas for new plugins and tools can be posted in [`remarkjs/ideas`][ideas].
A curated list of awesome remark resources can be found in [**awesome
remark**][awesome].
This project has a [Code of Conduct][coc].
By interacting with this repository, organisation, or community you agree to
abide by its terms.
## License
[MIT][license] Β© [Titus Wormer][author]
[build-badge]: https://img.shields.io/travis/remarkjs/remark.svg
[build]: https://travis-ci.org/remarkjs/remark
[coverage-badge]: https://img.shields.io/codecov/c/github/remarkjs/remark.svg
[coverage]: https://codecov.io/github/remarkjs/remark
[downloads-badge]: https://img.shields.io/npm/dm/remark-parse.svg
[downloads]: https://www.npmjs.com/package/remark-parse
[size-badge]: https://img.shields.io/bundlephobia/minzip/remark-parse.svg
[size]: https://bundlephobia.com/result?p=remark-parse
[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/join%20the%20community-on%20spectrum-7b16ff.svg
[chat]: https://spectrum.chat/unified/remark
[health]: https://github.com/remarkjs/.github
[contributing]: https://github.com/remarkjs/.github/blob/master/contributing.md
[support]: https://github.com/remarkjs/.github/blob/master/support.md
[coc]: https://github.com/remarkjs/.github/blob/master/code-of-conduct.md
[ideas]: https://github.com/remarkjs/ideas
[awesome]: https://github.com/remarkjs/awesome-remark
[license]: https://github.com/remarkjs/remark/blob/master/license
[author]: https://wooorm.com
[npm]: https://docs.npmjs.com/cli/install
[unified]: https://github.com/unifiedjs/unified
[data]: https://github.com/unifiedjs/unified#processordatakey-value
[remark]: https://github.com/remarkjs/remark/tree/master/packages/remark
[blocks]: https://github.com/remarkjs/remark/blob/master/packages/remark-parse/lib/block-elements.js
[mdast]: https://github.com/syntax-tree/mdast
[escapes]: https://spec.commonmark.org/0.29/#backslash-escapes
[node]: https://github.com/syntax-tree/unist#node
[parent]: https://github.com/syntax-tree/unist#parent
[position]: https://github.com/syntax-tree/unist#position
[parser]: https://github.com/unifiedjs/unified#processorparser
[transformer]: https://github.com/unifiedjs/unified#function-transformernode-file-next
[extend]: #extending-the-parser
[tokenizer]: #function-tokenizereat-value-silent
[locator]: #tokenizerlocatorvalue-fromindex
[eat]: #eatsubvalue
[add]: #addnode-parent
[announcement]: https://medium.com/unifiedjs/collectively-evolving-through-crowdsourcing-22c359ea95cc
[remark-disable-tokenizers]: https://github.com/zestedesavoir/zmarkdown/tree/master/packages/remark-disable-tokenizers
[xss]: https://en.wikipedia.org/wiki/Cross-site_scripting
[rehype]: https://github.com/rehypejs/rehype
[sanitize]: https://github.com/rehypejs/rehype-sanitize
