Parser for unified. Parses markdown to an mdast syntax tree. Used in the remark processor. Can be extended to change how markdown is parsed.
npm:
npm install remark-parsevar 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});Configure the processor to read markdown as input and process an
mdast syntax tree.
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).blocks(Array.<string>, default: list of block HTML elements);
hello ~~hi~~ worldGFM mode (default: true) turns on:
---
title: YAML is Cool
---
# YAML is CoolYAML mode (default: true) enables raw YAML front matter to be detected
at the top.
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.
Something something[^or something?].
And something else[^1].
[^1]: This reference footnote contains a paragraph...
* ...and a listFootnotes 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.
This is a
paragraph.Breaks mode (default: false) exposes newline characters inside
paragraphs as breaks.
<block>foo
</block>Blocks (default: a list of HTML block elements) exposes let’s users define block-level HTML elements.
Check out some_file_name.txtPedantic mode (default: false) turns on:
- Emphasis (
_alpha_) and importance (__bravo__) with underscores in words; - Unordered lists with different markers (
*,-,+); - If
commonmarkis 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).
Access to the parser, if you need it.
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;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.
Array of blockTokenizers names (string) specifying the order in
which they run.
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.
Array of inlineTokenizers names (string) specifying the order in
which they run.
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.
Node? = tokenizer(eat, value);boolean? = tokenizer(eat, value, silent).
eat(Function) — Eat, when applicable, an entity;value(string) — Value which may start an entity;silent(boolean, optional) — Whether to detect or consume.
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.
- 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.
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.
value(string) — Value which may contain an entity;fromIndex(number) — Position to start searching at.
Index at which an entity may start, and -1 otherwise.
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).
subvalue(string) - Value to eat.
add.
var add = eat('foo');
add({type: 'text', value: 'foo'});Add positional information to node and add it to parent.
node(Node) - Node to patch position on and insert;parent(Node, optional) - Place to addnodeto in the syntax tree. Defaults to the currently processed node.
The given node.
Get the positional information which would be patched on
node by add.
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
node(Node) - Node to patch position on and insert;parent(Node, optional) - Place to addnodeto in the syntax tree. Defaults to the currently processed node.
The given node.