markdown-it/README.md

# markdown-it

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> Markdown parser done right. Fast and easy to extend.

__[Live demo](https://markdown-it.github.io)__

- Supports the [CommonMark](http://commonmark.org/) spec +
  [syntax extensions](#syntax-extensions) + sugar (URL autolinking, typographer).
- Configurable syntax! You can add new rules and even replace existing ones.
- [High speed](#benchmark)!
- [Community plugins](https://www.npmjs.org/browse/keyword/markdown-it-plugin) on npm.


## Install

**node.js** & **bower**:

```bash
npm install markdown-it --save
bower install markdown-it --save
```

**browser (CDN):**

- [jsDeliver CDN](http://www.jsdelivr.com/#!markdown-it "jsDelivr CDN")


## Usage

```js
// 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:

```js
// 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:

```js
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](http://commonmark.org/) mode with the `commonmark` preset:

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

#### full

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

```js
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:

```js
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](https://help.github.com/articles/github-flavored-markdown/#tables) (GFM)
- [\<del>](https://help.github.com/articles/github-flavored-markdown/#strikethrough)
  (GFM strikethrough) - `~~deleted text~~`

Disabled by default:

- [\<sup>](http://johnmacfarlane.net/pandoc/README.html#superscripts-and-subscripts) - `19^th^`
- [\<sub>](http://johnmacfarlane.net/pandoc/README.html#superscripts-and-subscripts) - `H~2~0`
- [abbreviations](https://michelf.ca/projects/php-markdown/extra/#abbr)
- [footnotes](http://johnmacfarlane.net/pandoc/README.html#footnotes)
- __\<ins>__ - `++inserted text++` (experimental)
- __\<mark>__ - `==marked text==` (experimental)

__*__ Experimental extensions can be changed later for something like
[Critic Markup](http://criticmarkup.com/), but you will still be able to use
old-style rules via external plugins if you prefer.


### Manage rules

```js
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:

```js
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 ?.... → ?.., !.... → !..)
// ???????? → ???, !!!!! → !!!, `,,` → `,`
// -- → &ndash;, --- → &mdash;
//
```

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:

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

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


## References / Thanks

Big thanks to [John MacFarlane](https://github.com/jgm) 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:

```js
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):

```bash
$ 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](https://github.com/rlidwka)
- Vitaly Puzrin [github/puzrin](https://github.com/puzrin)


## License

[MIT](https://github.com/markdown-it/markdown-it/blob/master/LICENSE)