markdown-it

What is markdown-it?

The markdown-it npm package is a Markdown parser that can convert Markdown text into HTML. It is highly extensible and supports various plugins to enhance its functionality. It is commonly used to render user-generated content in web applications, documentation tools, and content management systems.

What are markdown-it's main functionalities?

Basic Markdown Parsing

This feature allows you to convert basic Markdown text into HTML. The code sample demonstrates how to create a new instance of MarkdownIt and use it to render a simple Markdown string.

const MarkdownIt = require('markdown-it');
const md = new MarkdownIt();
const result = md.render('# Markdown-it rulezz!');

HTML Output Customization

Markdown-it allows customization of the HTML output through options. The code sample shows how to enable HTML tags in source, automatically convert URLs to links, and use typographic replacements.

const MarkdownIt = require('markdown-it');
const md = new MarkdownIt({
  html: true,
  linkify: true,
  typographer: true
});

Syntax Extensions with Plugins

Markdown-it supports plugins to extend its syntax. The code sample demonstrates how to add emoji support to the Markdown parser using the markdown-it-emoji plugin.

const MarkdownIt = require('markdown-it');
const emojiPlugin = require('markdown-it-emoji');
const md = new MarkdownIt();
md.use(emojiPlugin);
const result = md.render('Hello :smile:');

Linkify

The linkify feature automatically detects URLs in the text and converts them into clickable links. The code sample shows how to enable this feature in the MarkdownIt instance.

const MarkdownIt = require('markdown-it');
const md = new MarkdownIt({
  linkify: true
});
const result = md.render('Visit https://www.example.com');

Other packages similar to markdown-it

marked

Marked is a fast Markdown parser and compiler built for speed. It is less extensible than markdown-it but is known for its performance and being a low-level compiler.

remarkable

Remarkable is another Markdown parser that claims to be very fast and efficient. It offers similar extensibility to markdown-it with a plugin system and is often used for its speed and comprehensive Markdown support.

showdown

Showdown is a JavaScript Markdown to HTML converter that can run both on the server and in the browser. It is often chosen for its client-side capabilities and extensibility with extensions.

README

markdown-it

Markdown parser done right. Fast and easy to extend.

Live demo

• Supports the CommonMark spec + syntax extensions + sugar (URL autolinking, typographer).
• Configurable syntax! You can add new rules and even replace existing ones.
• High speed!
• Community written plugins and utilities on npm.

Install

node.js & bower:

npm install markdown-it --save
bower install markdown-it --save

browser (CDN):

• jsDeliver CDN

Usage

// node.js, standard way:
var MarkdownIt = require('markdown-it'),
    md = new MarkdownIt();
console.log(md.render('# markdown-it rulezz!'));

// node.js, the same, but with sugar:
var md = require('markdown-it')();
console.log(md.render('# markdown-it rulezz!'));

// browser without AMD, added to "window" on script load
// Note, there are no dash.
var md = window.markdownit();
console.log(md.render('# markdown-it rulezz!'));

Options

By default markdown-it is configured to be similar to GFM, but with HTML disabled. This is easy to change if you prefer to use different settings.

There are two ways to define options.

constructor(preset, options)

• preset (String): "full"|"commonmark"|Optional.

Define options in the constructor:

// Actual default values
var md = require('markdown-it')({
  html:         false,        // Enable HTML tags in source
  xhtmlOut:     false,        // Use '/' to close single tags (<br />)
  breaks:       false,        // Convert '\n' in paragraphs into <br>
  langPrefix:   'language-',  // CSS language prefix for fenced blocks
  linkify:      false,        // Autoconvert URL-like text to links

  // Enable some language-neutral replacement + quotes beautification
  typographer:  false,

  // Double + single quotes replacement pairs, when typographer enabled,
  // and smartquotes on. Set doubles to '«»' for Russian, '„“' for German.
  quotes: '“”‘’',

  // Highlighter function. Should return escaped HTML,
  // or '' if the source string is not changed
  highlight: function (/*str, lang*/) { return ''; }
});

console.log(md.render('# markdown-it rulezz!'));
// => <h1>markdown-it rulezz!</h1>

.set

Or define options via the .set() method:

var md = require('markdown-it')();

md.set({
  html: true,
  breaks: true
});

Note: To achieve the best possible performance, don't modify a markdown-it instance on the fly. If you need multiple configurations it's best to create multiple instances and initialize each with a configuration that is ideal for that instance.

Presets

markdown-it offers some "presets" as a convenience to quickly enable/disable active syntax rules and options for common use cases.

commonmark

Enable strict CommonMark mode with the commonmark preset:

var md = require('markdown-it')('commonmark');

full

Enable all available rules (but still with default options, if not set):

var md = require('markdown-it')('full');

// Or with options:
var md = require('markdown-it')('full', {
  html: true,
  linkify: true,
  typographer: true
});

Syntax highlighting

Apply syntax highlighting to fenced code blocks with the highlight option:

var hljs       = require('highlight.js') // https://highlightjs.org/

// Actual default values
var md = require('markdown-it')({
  highlight: function (str, lang) {
    if (lang && hljs.getLanguage(lang)) {
      try {
        return hljs.highlight(lang, str).value;
      } catch (err) {}
    }

    try {
      return hljs.highlightAuto(str).value;
    } catch (err) {}

    return ''; // use external default escaping
  }
});

Syntax extensions

Enabled by default:

• Tables (GFM)
• <del> (GFM strikethrough) - ~~deleted text~~

Disabled by default:

• <sup> - 19^th^
• <sub> - H~2~0
• abbreviations
• footnotes
• <ins> - ++inserted text++ (experimental)
• <mark> - ==marked text== (experimental)

* Experimental extensions can be changed later for something like Critic Markup, but you will still be able to use old-style rules via external plugins if you prefer.

Manage rules

var md = require('markdown-it')();
md.inline.ruler.enable([ 'ins', 'mark' ]);
md.block.ruler.disable([ 'table' ]);

// Enable everything
md = require('markdown-it')('full', {
  html: true,
  linkify: true,
  typographer: true,
});

//
// Manually enable rules, disabled by default:
//
var md = require('markdown-it')();
md.block.ruler.core([
  'abbr'
]);
md.block.ruler.enable([
  'footnote',
  'deflist'
]);
md.block.ruler.enable([
  'footnote_inline',
  'ins',
  'mark',
  'sub',
  'sup'
]);

Typographer

Although full-weight typographical replacements are language specific, markdown-it provides coverage for the most common and universal use cases:

var md = require('markdown-it')({
  typographer: true,
  quotes: '“”‘’'
});

// Disable rules at all:
md.core.ruler.disable([ 'replacements', 'smartquotes' ]);

// Actual default replacements:
//
// '' → ‘’
// "" → “”. Set '«»' for Russian, '„“' for German, empty to disable
// (c) (C) → ©
// (tm) (TM) → ™
// (r) (R) → ®
// +- → ±
// (p) (P) -> §
// ... → … (also ?.... → ?.., !.... → !..)
// ???????? → ???, !!!!! → !!!, `,,` → `,`
// -- → –, --- → —
//

Of course, you can also add your own rules or replace the defaults with something more advanced or specific to your language.

Plugins

Easily load plugins with the .use() method:

var md = require('markdown-it')();

md.use(plugin1)
  .use(plugin2, opts)
  .use(plugin3);

References / Thanks

Big thanks to John MacFarlane for his work on the CommonMark spec and reference implementations. His work saved us a lot of time during this project's development.

Related Links:

1. https://github.com/jgm/CommonMark - reference CommonMark implementations in C & JS, also contains latest spec & online demo.
2. http://talk.commonmark.org - CommonMark forum, good place to collaborate developers' efforts.

Development / Modification

Parser consists of several responsibilities chains, filled with rules. You can reconfigure anyone as you wish. Render also can be modified and extended. See source code to understand details. Pay attention to these properties:

MarkdownIt.core
MarkdownIt.core.ruler
MarkdownIt.block
MarkdownIt.block.ruler
MarkdownIt.inline
MarkdownIt.inline.ruler
MarkdownIt.renderer
MarkdownIt.renderer.rules

Benchmark

Here is result of CommonMark spec parse at Core i5 2.4 GHz (i5-4258U):

$ benchmark/benchmark.js spec
Selected samples: (1 of 27)
 > spec

Sample: spec.txt (110610 bytes)
 > commonmark-reference x 40.42 ops/sec ±4.07% (51 runs sampled)
 > current x 74.99 ops/sec ±4.69% (67 runs sampled)
 > current-commonmark x 93.76 ops/sec ±1.23% (79 runs sampled)
 > marked-0.3.2 x 22.92 ops/sec ±0.79% (41 runs sampled)

As you can see, markdown-it doesn't pay with speed for it's flexibility. Because it's written in monomorphyc style and use JIT inline caches effectively.

Authors

• Alex Kocharin github/rlidwka
• Vitaly Puzrin github/puzrin

License

MIT

Changelog

[2.1.2] - 2014-12-23

Changed

• Exposed helpers into parser instances (for plugins).
• Removed utils from global export - been in instances seems enougth.
• Refactored demo & added markdown-it-emoji to it.