remark-parse

What is remark-parse?

The remark-parse package is a plugin for the Remark processor that parses Markdown content into a syntax tree. It is part of the unified ecosystem, which provides a way to parse, transform, and stringify content using abstract syntax trees (ASTs).

What are remark-parse's main functionalities?

Parsing Markdown

This feature allows you to parse Markdown content and transform it into an abstract syntax tree (AST). The code sample demonstrates how to use remark-parse with the remark library to parse a simple Markdown string.

const remark = require('remark');
const parse = require('remark-parse');

remark().use(parse).process('# Hello world!', function(err, file) {
  if (err) throw err;
  console.log(file);
});

Extensible Markdown Parsing

remark-parse can be extended with plugins to handle custom Markdown syntax. In this example, the 'remark-math' plugin is used to parse mathematical expressions within the Markdown content.

const remark = require('remark');
const parse = require('remark-parse');
const math = require('remark-math');

remark().use(parse).use(math).process('Euler's identity: $e^{i\pi} + 1 = 0$', function(err, file) {
  if (err) throw err;
  console.log(file);
});

Other packages similar to remark-parse

markdown-it

markdown-it is a Markdown parser with a similar goal to remark-parse, but it is implemented differently. It is often used for its speed and extensibility with plugins, and it can output HTML directly instead of an AST.

marked

marked is another Markdown parser that is known for being fast and lightweight. It is less extensible than remark-parse but can be a good choice for simpler use cases where a full AST is not required.

README

remark-parse

Parser for unified. Parses markdown to an mdast syntax tree. Used in the remark processor. Can be extended to change how markdown is parsed.

Installation

npm:

npm install remark-parse

Usage

var unified = require('unified');
var markdown = require('remark-parse');
var html = require('remark-html');

process.stdin
    .pipe(unified())
    .use(markdown)
    .use(html)
    .pipe(process.stdout, {
        'commonmark': true
    });

Table of Contents

• API
  • processor.use(parse)
  • parse.Parser
• Extending the Parser
  • Parser#blockTokenizers
  • Parser#blockMethods
  • Parser#inlineTokenizers
  • Parser#inlineMethods
  • function tokenizer(eat, value, silent)
  • tokenizer.locator(value, fromIndex)
  • eat(subvalue)
  • add(node[, parent])
  • add.test()
  • add.reset(node[, parent])
• License

API

processor.use(parse)

Configure the processor to read markdown as input and process an mdast syntax tree.

options

Options are passed later through processor.parse(), processor.process(), or processor.pipe(). The following settings are supported:

• gfm (boolean, default: true);
• yaml (boolean, default: true);
• commonmark (boolean, default: false);
• footnotes (boolean, default: false);
• pedantic (boolean, default: false);
• breaks (boolean, default: false).

options.gfm

hello ~~hi~~ world

GFM mode (default: true) turns on:

• Fenced code blocks;
• Autolinking of URLs;
• Deletions (strikethrough);
• Task lists;
• Tables.

options.yaml

---
title: YAML is Cool
---

# YAML is Cool

YAML mode (default: true) enables raw YAML front matter to be detected at the top.

options.commonmark

This is a paragraph
    and this is also part of the preceding paragraph.

CommonMark mode (default: false) allows:

• Empty lines to split blockquotes;
• Parentheses (( and )) around for link and image titles;
• Any escaped ASCII-punctuation character;
• Closing parenthesis ()) as an ordered list marker;
• URL definitions (and footnotes, when enabled) in blockquotes.

CommonMark mode disallows:

• Code 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 closing angle bracket (>), for lists, code, and thematicBreak.

options.footnotes

Something something[^or something?].

And something else[^1].

[^1]: This reference footnote contains a paragraph...

    * ...and a list

Footnotes mode (default: false) 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.breaks

This is a
paragraph.

Breaks mode (default: false) exposes newline characters inside paragraphs as breaks.

options.pedantic

Check out some_file_name.txt

Pedantic mode (default: false) 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 pedantic mode removes less spaces in list-items (at most four, instead of the whole indent).

parse.Parser

Access to the parser, if you need it.

Extending the Parser

Most often, using transformers to manipulate a syntax tree produces the desired output. Sometimes, mainly when introducing new syntactic entities with a certain level of precedence, interfacing with the parser is necessary.

If this plug-in is used, it adds a Parser constructor to the processor. Other plug-ins can add tokenizers to the parser’s prototype to change how markdown is parsed.

The below plug-in adds a tokenizer for at-mentions.

function mentions(processor) {
    var Parser = processor.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');
}

module.exports = mentions;

Parser#blockTokenizers

An object mapping tokenizer names to tokenizers. These tokenizers (for example: fencedCode, table, and paragraph) eat from the start of a value to a line ending.

Parser#blockMethods

Array of blockTokenizers names (string) specifying the order in which they run.

Parser#inlineTokenizers

An object mapping tokenizer names to tokenizers. These tokenizers (for example: url, reference, and emphasis) eat from the start of a value. To increase performance, they depend on locators.

Parser#inlineMethods

Array of inlineTokenizers names (string) specifying the order in which they run.

function tokenizer(eat, value, silent)

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]
            }]
        });
    }
}

tokenizeMention.notInLink = true;
tokenizeMention.locator = locateMention;

The parser knows two types of tokenizers: block level and inline level. Block level tokenizers are the same as inline level tokenizers, with the exception that the latter must have a locator.

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 “eating”. Locators enable tokenizers to function faster by providing information on where the next entity may occur.

Signatures

• Node? = tokenizer(eat, value);
• boolean? = tokenizer(eat, value, silent).

Parameters

• eat (Function) — Eat, when applicable, an entity;
• value (string) — Value which may start an entity;
• silent (boolean, optional) — Whether to detect or consume.

Properties

• locator (Function) — Required for inline tokenizers;
• onlyAtStart (boolean) — Whether nodes can only be found at the beginning of the document;
• notInBlock (boolean) — Whether nodes cannot be in blockquotes, lists, or footnote definitions;
• notInLink (boolean) — Whether nodes cannot be in lists.
• notInLink (boolean) — Whether nodes cannot be in links.

Returns

• In silent mode, whether a node can be found at the start of value;
• In normal mode, a node if it can be found at the start of value.

tokenizer.locator(value, fromIndex)

function locateMention(value, fromIndex) {
    return value.indexOf('@', fromIndex);
}

Locators are required for inline tokenization to keep the process performant. Locators enable inline tokenizers to function faster by providing information on the where the next entity occurs. Locators may be wrong, it’s OK if there actually isn’t a node to be found at the index they return, but they must skip any nodes.

Parameters

• value (string) — Value which may contain an entity;
• fromIndex (number) — Position to start searching at.

Returns

Index at which an entity may start, and -1 otherwise.

eat(subvalue)

var add = eat('foo');

Eat subvalue, which is a string at the start of the tokenized value (it’s tracked to ensure the correct value is eaten).

Parameters

• subvalue (string) - Value to eat.

Returns

add.

add(node[, parent])

var add = eat('foo');
add({type: 'text', value: 'foo'});

Add positional information to node and add it to parent.

Parameters

• node (Node) - Node to patch position on and insert;
• parent (Node, optional) - Place to add node to in the syntax tree. Defaults to the currently processed node.

Returns

The given node.

add.test()

Get the positional information which would be patched on node by add.

Returns

Location.

add.reset(node[, parent])

add, but resets the internal location. Useful for example in lists, where the same content is first eaten for a list, and later for list items

Parameters

• node (Node) - Node to patch position on and insert;
• parent (Node, optional) - Place to add node to in the syntax tree. Defaults to the currently processed node.

Returns

The given node.

License

MIT © Titus Wormer