turndown

by domchristie

domchristie / turndown

🛏 An HTML to Markdown converter written in JavaScript

5.2K Stars 648 Forks Last release: 22 days ago (v7.0.1) MIT License 412 Commits 46 Releases

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Turndown

Build Status

Convert HTML into Markdown with JavaScript.

to-markdown has been renamed to Turndown. See the migration guide for details.

Installation

npm:

npm install turndown

Browser:


For usage with RequireJS, UMD versions are located in

lib/turndown.umd.js
(for Node.js) and
lib/turndown.browser.umd.js
for browser usage. These files are generated when the npm package is published. To generate them manually, clone this repo and run
npm run build
.

Usage

// For Node.js
var TurndownService = require('turndown')

var turndownService = new TurndownService() var markdown = turndownService.turndown('

Hello world!

')

Turndown also accepts DOM nodes as input (either element nodes, document nodes, or document fragment nodes):

var markdown = turndownService.turndown(document.getElementById('content'))

Options

Options can be passed in to the constructor on instantiation. For example:

var turndownService = new TurndownService({ option: 'value' })

| Option | Valid values | Default | | :-------------------- | :------------ | :------ | |

headingStyle
|
setext
or
atx
|
setext
| |
hr
| Any Thematic break |
* * *
| |
bulletListMarker
|
-
,
+
, or
*
|
*
| |
codeBlockStyle
|
indented
or
fenced
|
indented
| |
fence
|
` or `~~~` | `
 |
| 
emDelimiter
|
_
or
*
|
_
| |
strongDelimiter
|
**
or
__
|
**
| |
linkStyle
|
inlined
or
referenced
|
inlined
| |
linkReferenceStyle
|
full
,
collapsed
, or
shortcut
|
full
|

Advanced Options

| Option | Valid values | Default | | :-------------------- | :------------ | :------ | |

blankReplacement
| rule replacement function | See Special Rules below | |
keepReplacement
| rule replacement function | See Special Rules below | |
defaultReplacement
| rule replacement function | See Special Rules below |

Methods

addRule(key, rule)

The

key
parameter is a unique name for the rule for easy reference. Example:
turndownService.addRule('strikethrough', {
  filter: ['del', 's', 'strike'],
  replacement: function (content) {
    return '~' + content + '~'
  }
})

addRule
returns the
TurndownService
instance for chaining.

See Extending with Rules below.

keep(filter)

Determines which elements are to be kept and rendered as HTML. By default, Turndown does not keep any elements. The filter parameter works like a rule filter (see section on filters belows). Example:

turndownService.keep(['del', 'ins'])
turndownService.turndown('

Hello worldWorld

') // 'Hello worldWorld'

This will render

and
elements as HTML when converted.

keep
can be called multiple times, with the newly added keep filters taking precedence over older ones. Keep filters will be overridden by the standard CommonMark rules and any added rules. To keep elements that are normally handled by those rules, add a rule with the desired behaviour.

keep
returns the
TurndownService
instance for chaining.

remove(filter)

Determines which elements are to be removed altogether i.e. converted to an empty string. By default, Turndown does not remove any elements. The filter parameter works like a rule filter (see section on filters belows). Example:

turndownService.remove('del')
turndownService.turndown('

Hello worldWorld

') // 'Hello World'

This will remove

elements (and contents).

remove
can be called multiple times, with the newly added remove filters taking precedence over older ones. Remove filters will be overridden by the keep filters, standard CommonMark rules, and any added rules. To remove elements that are normally handled by those rules, add a rule with the desired behaviour.

remove
returns the
TurndownService
instance for chaining.

use(plugin|array)

Use a plugin, or an array of plugins. Example:

// Import plugins from turndown-plugin-gfm
var turndownPluginGfm = require('turndown-plugin-gfm')
var gfm = turndownPluginGfm.gfm
var tables = turndownPluginGfm.tables
var strikethrough = turndownPluginGfm.strikethrough

// Use the gfm plugin turndownService.use(gfm)

// Use the table and strikethrough plugins only turndownService.use([tables, strikethrough])

use
returns the
TurndownService
instance for chaining.

See Plugins below.

Extending with Rules

Turndown can be extended by adding rules. A rule is a plain JavaScript object with

filter
and
replacement
properties. For example, the rule for converting

elements is as follows:
{
  filter: 'p',
  replacement: function (content) {
    return '\n\n' + content + '\n\n'
  }
}

The filter selects

elements, and the replacement function returns the

contents separated by two new lines.

filter
String|Array|Function

The filter property determines whether or not an element should be replaced with the rule's

replacement
. DOM nodes can be selected simply using a tag name or an array of tag names:
  • filter: 'p'
    will select

    elements
  • filter: ['em', 'i']
    will select
    or
    elements

Alternatively, the filter can be a function that returns a boolean depending on whether a given node should be replaced. The function is passed a DOM node as well as the

TurndownService
options. For example, the following rule selects
elements (with an
href
) when the
linkStyle
option is
inlined
:
filter: function (node, options) {
  return (
    options.linkStyle === 'inlined' &&
    node.nodeName === 'A' &&
    node.getAttribute('href')
  )
}

replacement
Function

The replacement function determines how an element should be converted. It should return the Markdown string for a given node. The function is passed the node's content, the node itself, and the

TurndownService
options.

The following rule shows how

elements are converted:
rules.emphasis = {
  filter: ['em', 'i'],

replacement: function (content, node, options) { return options.emDelimiter + content + options.emDelimiter } }

Special Rules

Blank rule determines how to handle blank elements. It overrides every rule (even those added via

addRule
). A node is blank if it only contains whitespace, and it's not an
,
,
 or a void element. Its behaviour can be customised using the 
blankReplacement
option.

Keep rules determine how to handle the elements that should not be converted, i.e. rendered as HTML in the Markdown output. By default, no elements are kept. Block-level elements will be separated from surrounding content by blank lines. Its behaviour can be customised using the

keepReplacement
option.

Remove rules determine which elements to remove altogether. By default, no elements are removed.

Default rule handles nodes which are not recognised by any other rule. By default, it outputs the node's text content (separated by blank lines if it is a block-level element). Its behaviour can be customised with the

defaultReplacement
option.

Rule Precedence

Turndown iterates over the set of rules, and picks the first one that matches the

filter
. The following list describes the order of precedence:
  1. Blank rule
  2. Added rules (optional)
  3. Commonmark rules
  4. Keep rules
  5. Remove rules
  6. Default rule

Plugins

The plugin API provides a convenient way for developers to apply multiple extensions. A plugin is just a function that is called with the

TurndownService
instance.

Escaping Markdown Characters

Turndown uses backslashes (

\
) to escape Markdown characters in the HTML input. This ensures that these characters are not interpreted as Markdown when the output is compiled back to HTML. For example, the contents of

1. Hello world

needs to be escaped to
1\. Hello world
, otherwise it will be interpreted as a list item rather than a heading.

To avoid the complexity and the performance implications of parsing the content of every HTML element as Markdown, Turndown uses a group of regular expressions to escape potential Markdown syntax. As a result, the escaping rules can be quite aggressive.

Overriding
TurndownService.prototype.escape

If you are confident in doing so, you may want to customise the escaping behaviour to suit your needs. This can be done by overriding

TurndownService.prototype.escape
.
escape
takes the text of each HTML element and should return a version with the Markdown characters escaped.

Note: text in code elements is never passed to

escape
.

License

turndown is copyright © 2017+ Dom Christie and released under the MIT license.

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