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https://github.com/yogthos/markdown-clj

Markdown parser in Clojure
https://github.com/yogthos/markdown-clj
clojure-library clojurescript markdown-parser
Last synced: 4 days ago
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Markdown parser in Clojure
Host: GitHub
URL: https://github.com/yogthos/markdown-clj
Owner: yogthos
License: epl-1.0
Created: 2011-10-10T21:45:56.000Z (over 13 years ago)
Default Branch: master
Last Pushed: 2024-11-02T12:17:13.000Z (2 months ago)
Last Synced: 2024-12-31T18:09:19.287Z (11 days ago)
Topics: clojure-library, clojurescript, markdown-parser
Language: Clojure
Homepage:
Size: 1.41 MB
Stars: 548
Watchers: 13
Forks: 121
Open Issues: 26
Metadata Files:
- Readme: README.md
- Funding: .github/FUNDING.yml
- License: LICENSE
Awesome Lists containing this project

my-awesome-github-stars - yogthos/markdown-clj - Markdown parser in Clojure (Clojure)
awesome-clojurescript - markdown-clj
README

        # Markdown parser written in Clojure/Script

[![CircleCI](https://circleci.com/gh/yogthos/markdown-clj.svg?style=svg)](https://circleci.com/gh/yogthos/markdown-clj) [![Downloads](https://jarkeeper.com/yogthos/markdown-clj/downloads.svg)](https://jarkeeper.com/yogthos/markdown-clj)

## Demo

You can try out the parser [here](https://rawgit.com/yogthos/markdown-clj/master/demo/markdown.html).

## Building Js artifact

run `lein with-profile js cljsbuild once` this will create a standalone `js/markdown.js` artifact.

## Installation

A markdown parser that compiles to both Clojure and ClojureScript.

[![Clojars Project](http://clojars.org/markdown-clj/latest-version.svg)](http://clojars.org/markdown-clj)

Note: `markdown-clj` versions prior to `0.9.68` requires Clojure 1.2+ to run, versions `0.9.68+` require Clojure 1.7.

[![NPM](https://nodei.co/npm/markdown-clj.png?mini=true)](https://www.npmjs.com/package/markdown-clj)

## Usage Clojure

Markdown-clj can be invoked either by calling `md-to-html` or `md-to-html-string` functions.

The `md-to-html` function accepts an input containing Markdown markup and an output where

the resulting HTML will be written. The input and output parameters will be passed to a reader

and a writer respectively:

```clojure

(ns foo

  (:use markdown.core))

(md-to-html "input.md" "output.html")

(md-to-html (input-stream "input.md") (output-stream "test.txt"))

```

The `md-to-html-string` function accepts a string with markdown content and returns a string with the resulting HTML:

```clojure

(md-to-html-string "# This is a test\nsome code follows\n```clojure\n(defn foo [])\n```")

```

```xml

 This is a test
some code follows(defn foo [])



```

Both `md-to-html` and `md-to-html-string` accept optional parameters:

Specifying `:heading-anchors` will create anchors for the heading tags, eg:

```clojure

(markdown/md-to-html-string "###foo bar BAz" :heading-anchors true)

```

```xml

foo bar BAz

```

The code blocks default to a [highlight.js](https://highlightjs.org/) compatible format of:

```xml

some code

```

Specifying `:code-style` will override the default code class formatting for code blocks, eg:

```clojure

(md-to-html-string "# This is a test\nsome code follows\n```clojure\n(defn foo [])\n```"

                   :code-style #(str "class=\"brush: " % "\""))

```

```xml

 This is a test
some code follows

(defn foo [])



```

Specifying `:pre-style` will override the default pre class formatting.

```clojure

(md-to-html-string "# This is a test\nsome code follows\n```clojure\n(defn foo [])\n```"

                   :pre-style #(str "class=\"brush: " % "\""))

```

```xml

 This is a test
some code follows

(defn foo [])



```

### Reference style links

The parser defaults to using inline reference for performance reasons, to enable reference style links pass in the `:reference-links? true` option:

```clojure

(md-to-html-string

  "This is [an example][id] reference-style link.

   [id]: http://example.com/ 'Optional Title Here'"

   :reference-links? true)

```

### Footnotes

To enable footnotes, pass the `:footnotes? true` option:

```clojure

(md-to-html-string

  "Footnotes will appear automatically numbered with a link to the footnote at bottom of the page [^footnote1].

  [^footnote1]: The footnote will contain a back link to to the referring text."

  :footnotes? true)

```

### Metadata

The metadata encoded using the syntax described by [MultiMarkdown](https://github.com/fletcher/MultiMarkdown/wiki/MultiMarkdown-Syntax-Guide#metadata) can be optionally extracted from the document.

The `md-to-html` function will attempt to parse the metadata when passed the `:parse-meta? true` option and return it as its output.

Additionally, `md-to-html-string-with-meta` function can be used to parse string input. The function returns a map with two keys, `:html` containing the parsed HTML, and `:metadata` containing a map with the metadata included at the top of the document.

To parse *only* the metadata, use `md-to-meta`.  This function returns a metadata map for the given input, but does not otherwise parse the Markdown or return HTML. It can run more quickly than either of the functions that return HTML and can be useful in scenarios where the metadata can be useful by itself.

The value of each key in the metadata map will be a list of either 0, 1 or many strings. If a metadata value ends in two spaces then the string will end in a newline. If a line does not contain a header and has at least 4 spaces in front of it then it will be considered to be a member of the last key that was found.

```clojure

(let [input    (new StringReader text)

      output   (new StringWriter)

      metadata (md-to-html input output :parse-meta? true)

      html     (.toString output)]

  {:metadata metadata :html html})

(md-to-html-string-with-meta

  "Author: Rexella van Imp

    Kim Jong-un

Date: October 31, 2015

   # Hello!")

{:metadata {:author ["Rexella van Imp"

                     "Kim Jong-un"],

            :date ["October 31, 2015"]},

 :html "
Hello!"}

```

### Selectively inhibiting the Parser

If you pass `:inhibit-separator "some-string"`, then any text within occurrences of `some-string` will be output verbatim, eg:

```clojure

(md-to-html-string "For all %$a_0, a_1, ..., a_n in R$% there is _at least one_ %$b_n in R$% such that..."

                   :inhibit-separator "%")

```

```xml

For all $a_0, a_1, ..., a_n in R$ there is at least one $b_n in R$ such that...

```

This may be useful to use `markdown-clj` along with other parsers of languages with conflicting syntax (e.g. asciimath2jax).

If you need to output the separator itself, enter it twice without any text inside.  Eg:

```clojure

(md-to-html-string "This is one of those 20%% vs 80%% cases."

                   :inhibit-separator "%")

```

```xml

This is one of those 20% vs 80% cases.

```

Some caveats:

- Like other tags, this only works within a single line.

- If you remove the default transformers with `:replacement-transformers` (which see below), inhibiting will stop working.

- Currently, dashes (`--` and `---`) can't be suppressed this way.

## Customizing the Parser

Additional transformers can be specified using the `:custom-transformers` key.

A transformer function must accept two arguments.

First argument is the string representing the current line and the second is the map representing the current state.

The default state keys are:

* `:code` - inside a code section

* `:codeblock` - inside a code block

* `:eof` - end of file

* `:heading` - in a heading

* `:hr` - in a horizontal line

* `:lists` - inside a list

* `:blockquote` - inside a blockquote

* `:paragraph` - in a paragraph

* `:last-line-empty?` - was last line an empty line?

For example, if we wanted to add a transformer that would capitalize all text we could do the following:

```clojure

(defn capitalize [text state]

  [(.toUpperCase text) state])

(markdown/md-to-html-string "#foo" :custom-transformers [capitalize])

```

```xml

FOO

```

Alternatively, you could provide a custom set of transformers to replace the default transformers using the `:replacement-transformers` key.

```clojure

(markdown/md-to-html-string "#foo" :replacement-transformers [capitalize])

```

This can also be used to add preprocessor transformers. For example, if we wanted to sanitize any image links and escape HTML we could do the following:

```clojure

(use 'markdown.transformers 'markdown.core)

(defn escape-images [text state]

  [(clojure.string/replace text #"(!\[.*?\]\()(.+?)(\))" "") state])

(defn escape-html

    "Change special characters into HTML character entities."

    [text state]

    [(if-not (or (:code state) (:codeblock state))

       (clojure.string/escape

         text

         {\& "&"

          \< "<"

          \> ">"

          \" """

          \' "'"})

       text) state])

       

(markdown/md-to-html-string

  "
escapedfoo ![Alt text](/path/to/img.jpg \"Optional Title\") bar [text](http://test)"

  :replacement-transformers (into [escape-images escape-html] transformer-vector))

```

```xml

"
<h1>escaped</h1>foo  bar text"

```

### Codeblock callbacks

It's possible to pass a `:codeblock-callback` function to the parser that will

postprocess the code as follows: 

You can also pass `:codeblock-no-escape? true` to disable code escaping.

```clojure

(markdown/md-to-html-string "```python\ndef f(x):\n    return x * 2\n```"

                       :codeblock-no-escape? true

                       :codeblock-callback (fn

                                             [code language]

                                             (clygments/highlight code language :html)))

```

## Usage ClojureScript

The ClojureScript portion works the same as above except that the entry function is called `md->html`. It accepts

a string followed by the options as its input, and returns the resulting HTML string:

```clojure

(ns myscript

  (:require [markdown.core :refer [md->html]]))

(.log js/console

  (md->html "##This is a heading\nwith a paragraph following it"))

(.log js/console

  (md->html "# This is a test\nsome code follows\n```clojure\n(defn foo [])\n```"

               :code-style #(str "class=\"" % "\"")))

(md->html-with-meta "# This is a test\nsome code follows\n```clojure\n(defn foo [])\n```")

```

## Usage JavaScript

```javascript

console.log(markdown.core.mdToHtml("##This is a heading\nwith a paragraph following it"));

// With keyword arguments

console.log(markdown.core.mdToHtml("##This is a heading\nwith a paragraph following it", "heading-anchors", true));

```

## Supported syntax

Control characters can be escaped using \

```

\\ backslash

\` backtick

\* asterisk

\_ underscore

\{ curly braces

\}

\[ square brackets

\]

\( parentheses

\)

\# hash mark

\+ plus sign

\- minus sign (hyphen)

\. dot

\! exclamation mark

\^ caret / circumflex accent

```

#### Basic Elements

[Blockquote](#blockquote),

[Strong](#strong),

[Bold](#bold),

[Bold-Italic](#bold-italic),

[Emphasis](#emphasis),

[Italics](#italics),

[Heading](#heading),

[Line](#line),

[Linebreak](#linebreak),

[Paragraph](#paragraph),

[Strikethrough](#strikethrough)

#### Links

[Image](#image),

[Link](#link)

##### Automatic Links

This is a shortcut style for creating “automatic” links for URLs and email addresses:

```

```

will be turned this into:

```

http://example.com/

```

Automatic links for email addresses work similarly, except that they are hex encoded:

```



```

will be turned into:

```

[email protected]

```

#### Lists

[Ordered List](#ordered-list),

[Unordered List](#unordered-list)

#### Code

[Code Block](#code-block),

[Indented Code](#indented-code),

[Inline Code](#inline-code)

***

### Heading

the number of hashes indicates the level of the heading

```

# Heading

##Sub-heading

### Sub-sub-heading

```

headings can also be defined using `=` and `-` for `h1` and `h2` respectively

```

Heading 1

=========

Heading 2

---------

```

### Line

```

***

* * *

*****

- - -

______

```

### Linebreak

If a line ends with two or more spaces a `
` tag will be inserted at the end.

### Emphasis

```

*foo*

```

### Italics

```

_foo_

```

### Strong

```

**foo**

```

### Bold

```

__foo__

```

### Bold-Italic

```

***bold italic***

```

### Blockquote

`>` prefixes regular blockquote paragraphs.  `>-` prefixes a

blockquote footer that can be used for author attribution.

```

>This is a blockquote

with some content

>this is another blockquote

> Everyone thinks of changing the world,

but no one thinks of changing himself.

>- Leo Tolstoy

```

### Paragraph

```

This is a paragraph, it's

split into separate lines.

This is another paragraph.

```

### Unordered List

indenting an item makes it into a sublist of the item above it, ordered and unordered lists can be nested within one another.

List items can be split over multiple lines.

```

* Foo

* Bar

 * Baz

```

```

* foo

* bar

   * baz

     1. foo

     2. bar

        more content

        ## subheading

        ***

        **strong text** in the list

   * fuzz

      * blah

      * blue

* brass

```

### Ordered List

```

1. Foo

2. Bar

3. Baz

```

### Inline Code

Any special characters in code will be escaped with their corresponding HTML codes.

```

Here's some code `x + y = z` that's inlined.

```

### Code block

Using three backquotes indicates a start of a code block, the next three backquotes ends the code block section.

Optionally, the language name can be put after the backquotes to produce a tag compatible with [highlight.js](https://highlightjs.org/), eg:

```clojure

(defn foo [bar] "baz")

```

### Indented Code

indenting by at least 4 spaces creates a code block

    some

    code

    here

note: XML is escaped in code sections

### Strikethrough

```

~~foo~~

```

### Superscript

```

a^2 + b^2 = c^2

```

### Link

```

[github](http://github.com)

```

##### Reference Link

```

This is [an example][id] reference-style link.

[id]: http://example.com/  "Optional Title Here"

```

note: reference links require the `:reference-links?` option to be set to true

### Footnote

```

"Footnotes will appear automatically numbered with a link to the footnote at bottom of the page [^footnote1].

[^footnote1]: The footnote will contain a back link to to the referring text."

```

note: to enable footnotes, the `:footnotes?` option must be set to true.

### Image

```

![Alt text](http://server/path/to/img.jpg)

![Alt text](/path/to/img.jpg "Optional Title")

```

##### Image Reference

```

This is ![an example][id] reference-style image descriptor.

[id]: http://example.com/  "Optional Title Here"

```

note: reference links require the `:reference-links?` option to be set to true

### Image Link

```

[![Continuous Integration status](https://secure.travis-ci.org/yogthos/markdown-clj.png)](http://travis-ci.org/yogthos/markdown-clj)

```

### Table

You can create tables by assembling a list of words and dividing them with hyphens - (for the first row), and then separating each column with a pipe |:

```

| First Header  | Second Header |

| ------------- | ------------- |

| Content Cell  | Content Cell  |

| Content Cell  | Content Cell  |

```

By including colons : within the header row, you can define text to be left-aligned, right-aligned, or center-aligned:

```

| Left-Aligned  | Center Aligned    | Right Aligned |

| :------------ | :---------------: | ------------: |

| col 3 is      |  some wordy text  | $1600         |

| col 2 is      |  centered         |   $12         |

| zebra stripes |  are neat         |    $1         |

```

A colon on the left-most side indicates a left-aligned column; a colon on the right-most side indicates a right-aligned column; a colon on both sides indicates a center-aligned column.

## Limitations

The parser reads the content line by line, this means that tag content is not allowed to span multiple lines.

## License

Copyright © 2015 Dmitri Sotnikov

Distributed under the Eclipse Public License, the same as Clojure.