Markdown Preprocessor (MarkdownPP)

The Markdown Preprocessor is a JavaScript rewrite of John Reese's Python module, designed to add extended features on top of the excellent Markdown syntax defined by John Gruber. These additions are mainly focused on creating larger technical documents without needing to use something as heavy and syntactically complex as Docbook.

MarkdownPP uses a set of selectable modules to apply a series of transforms to the original document, with the end goal of generating a new Markdown document that contains sections or features that would be laborious to generate or maintain by hand.

Documents designed to be preprocessed by MarkdownPP should try to follow the convention of naming files with a .mdpp extension, so that MarkdownPP can generate a document with the same name, but with the standard .md extension. As an example, this document in raw format is named "readme.mdpp", and the generated document from MarkdownPP is named "readme.md" so that GitHub can find and process that document when viewing the repository.

1. Installation and Usage
2. Modules
2.1. Includes
2.2. IncludeURLs
2.3. Table of Contents
2.4. Reference
2.5. LaTeX Rendering
2.6. YouTube Embeds
3. Examples
4. Support
5. References

1. Installation and Usage

You can download or clone the source code from GitHub, or you can install from the npm repository with:

npm install markdown-pp-js --save

or

yarn install markdown-pp-js --saved

There are two components to the project: a JavaScript module, index.js, and a a simple command line interface to the module, markdownpp.

Assuming you have a file named foo.mdpp, you can generate the preprocessed file foo.md by running the following command:

$ node markdownpp foo.mdpp -o foo.md

If you do not specify an output file name, the results will be printed to stdout, enabling them to be piped to another command.

By default, all available modules are enabled. You can specify a list of modules to exclude:

$ node markdownpp foo.mdpp -o foo.md -e latexrender,youtubembed

To see usage instructions, including a list of enabled modules, supply the -h or --help arguments:

$ node markdownpp --help

2. Modules

2.1. Includes

In order to facilitate large documentation projects, MarkdownPP has an Include module that will replace a line of the form !INCLUDE "path/to/filename" with the contents of that file, recursively including other files as needed.

File foo.mdpp:

Hello

File bar.mdpp:

World!

File index.mdpp:

!INCLUDE "foo.mdpp"
!INCLUDE "bar.mdpp"

Compiling index.mdpp with the Include module will produce the following:

Hello
World!

Furthermore, the Include module supports the shifting of headers in the file to be included. For example,

File foo.mdpp:

# Foo
## Bar

File index.mdpp:

# Title
## Subtitle
!INCLUDE "foo.mdpp", 2

Compiling index.mdpp with the Include module and using 2 as shift parameter will yield:

# Title
## Subtitle
### Foo
#### Bar

2.2. IncludeURLs

Facilitates the inclusion of remote files, such as files kept in a subversion or GitHub repository. Like Include, the IncludeURL module can replace a line of the form !INCLUDEURL "http://your.domain/path/to/filename" with the contents returned from that url, recursively including additional remote urls as needed.

IncludeURL runs immediately after the Include module finishes executing. This means that is it possible to include local files that then require remote files, but impossible parse !INCLUDE statements found in remote files. This is prevent ambiguity as to where the file would be located.

Remote file http://your.domain/foo.mdpp:

Hello

Remote file http://your.domain/bar.mdpp:

Remote World!

Local file index.mdpp:

!INCLUDEURL "http://your.domain/foo.mdpp"
!INCLUDEURL "http://your.domain/bar.mdpp"

Compiling index.mdpp with the IncludeURL module will produce the following:

Hello
Remote World!

2.3. Table of Contents

The biggest feature provided by MarkdownPP is the generation of a table of contents for a document, with each item linked to the appropriate section of the markup. The table is inserted into the document wherever the preprocessor finds !TOC at the beginning of a line. Named <a> tags are inserted above each Markdown header, and the headings are numbered hierarchically based on the heading tag that Markdown would generate.

2.4. Reference

Similarly, MarkdownPP can generate a list of references that follow Markdown's alternate link syntax, eg [name]: <url> "Title". A list of links will be inserted wherever the preprocessor finds a line beginning with !REF. The generated reference list follows the same alternate linking method to ensure consistency in your document, but the link need not be referenced anywhere in the document to be included in the list.

2.5. LaTeX Rendering

Lines and blocks of lines beginning and ending with $ are rendered as LaTeX, using Google's charting engine.

For example,

$\displaystyle \int x^2 = \frac{x^3}{3} + C$

becomes

2.6. YouTube Embeds

As GitHub-flavored Markdown does not allow embed tags, each line of the form !VIDEO "[youtube url]" is converted into a screenshot that links to the video, roughly simulating the look of an embedded video player.

For example,

!VIDEO "http://www.youtube.com/embed/7aEYoP5-duY"

becomes

3. Examples

Example file.mdpp:

# Document Title

!TOC

## Header 1
### Header 1.a
## Header 2

!REF

[github]: http://github.com "GitHub"

The preprocessor would generate the following Markdown-ready document file.md:

# Document Title

1\. [Header 1](#header1)
1.1\. [Header 1.a](#header1a)
2\. [Header 2](#header2)

<a name="header1"></a>
## Header 1
<a name="header1a"></a>
### Header 1.a
<a name="header2"></a>
## Header 2

*	[GitHub][github]

[github]: http://github.com "GitHub"

4. Support

If you find any problems with MarkdownPP, or have any feature requests, please report them to GitHub, and I will respond when possible. Code contributions are always welcome, and ideas for new modules, or additions to existing modules, are also appreciated.

5. References

• Markdown Preprocessor on GitHub