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A Markdown parser for javascript

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markdown-js

Yet another Markdown parser, this time for JavaScript. There's a few options that precede this project but they all treat Markdown to HTML conversion as a single step process. You pass Markdown in and get HTML out, end of story. We had some pretty particular views on how the process should actually look, which include:

  • Producing well-formed HTML. This means that em and strong nesting is important, as is the ability to output as both HTML and XHTML
  • Having an intermediate representation to allow processing of parsed data (we in fact have two, both JsonML: a markdown tree and an HTML tree)
  • Being easily extensible to add new dialects without having to rewrite the entire parsing mechanics
  • Having a good test suite. The only test suites we could find tested massive blocks of input, and passing depended on outputting the HTML with exactly the same whitespace as the original implementation

Installation

Just the markdown library:

npm install markdown

Optionally, install md2html into your path

npm install -g markdown

In the browser

If you want to use from the browser go to the releases page on GitHub and download the version you want (minified or not).

Usage

 Node

The simple way to use it with Node is:

var markdown = require( "markdown" ).markdown;
console.log( markdown.toHTML( "Hello *World*!" ) );

 Browser

It also works in a browser; here is a complete example:

<!DOCTYPE html>
<html>
  <body>
    <textarea id="text-input" oninput="this.editor.update()"
              rows="6" cols="60">Type **Markdown** here.</textarea>
    <div id="preview"> </div>
    <script src="lib/markdown.js"></script>
    <script>
      function Editor(input, preview) {
        this.update = function () {
          preview.innerHTML = markdown.toHTML(input.value);
        };
        input.editor = this;
        this.update();
      }
      var $ = function (id) { return document.getElementById(id); };
      new Editor($("text-input"), $("preview"));
    </script>
  </body>
</html>

Command Line

Assuming you've installed the md2html script (see Installation, above), you can convert Markdown to HTML:

# read from a file
md2html /path/to/doc.md > /path/to/doc.html

# or from stdin
echo 'Hello *World*!' | md2html

 More Options

If you want more control check out the documentation in the .js files under src/ which details all the methods and parameters available (including examples!). One day we'll get the docs generated and hosted somewhere for nicer browsing.

Meanwhile, here's an example of using the multi-step processing to make wiki-style linking work by filling in missing link references:

var md = require( "markdown" ).markdown,
    text = "[Markdown] is a simple text-based [markup language]\n" +
           "created by [John Gruber]\n\n" +
           "[John Gruber]: http://daringfireball.net";

// parse the markdown into a tree and grab the link references
var tree = md.parse( text ),
    refs = tree[ 1 ].references;

// iterate through the tree finding link references
( function find_link_refs( jsonml ) {
  if ( jsonml[ 0 ] === "link_ref" ) {
    var ref = jsonml[ 1 ].ref;

    // if there's no reference, define a wiki link
    if ( !refs[ ref ] ) {
      refs[ ref ] = {
        href: "http://en.wikipedia.org/wiki/" + ref.replace(/\s+/, "_" )
      };
    }
  }
  else if ( Array.isArray( jsonml[ 1 ] ) ) {
    jsonml[ 1 ].forEach( find_link_refs );
  }
  else if ( Array.isArray( jsonml[ 2 ] ) ) {
    jsonml[ 2 ].forEach( find_link_refs );
  }
} )( tree );

// convert the tree into html
var html = md.renderJsonML( md.toHTMLTree( tree ) );
console.log( html );

Intermediate Representation

Internally the process to convert a chunk of Markdown into a chunk of HTML has three steps:

  1. Parse the Markdown into a JsonML tree. Any references found in the parsing are stored in the attribute hash of the root node under the key references.
  2. Convert the Markdown tree into an HTML tree. Rename any nodes that need it (bulletlist to ul for example) and lookup any references used by links or images. Remove the references attribute once done.
  3. Stringify the HTML tree being careful not to wreck whitespace where whitespace is important (surrounding inline elements for example).

Each step of this process can be called individually if you need to do some processing or modification of the data at an intermediate stage. For example, you may want to grab a list of all URLs linked to in the document before rendering it to HTML which you could do by recursing through the HTML tree looking for a nodes.

Building and Testing markdown-js

We use Grunt to build and run markdown-js's tests. Make sure you run npm install to install the developer dependencies for the project, then you can:

$ npm test

To run our test suite. If you'd like to build markdown-js, you can run:

$ ./node_modules/.bin/grunt all

This command will run all the tests, then output a concatenated markdown.js and markdown.min.js in the dist/ directory for use in a browser application.

Building a custom markdown-js

By default, you will get the Gruber and Maruku dialects included when you run grunt all. However, you can create a custom build using the following syntax if you don't want to include Maruku support.

$ ./node_modules/.bin/grunt "custom:-dialects/maruku"

Running Tests

To run the tests under Node you will need tap installed (it's listed as a devDependencies so npm install from the checkout should be enough), then do

$ npm test

Contributing

Do the usual GitHub fork and pull request dance. Add yourself to the contributors section of package.json too if you want to.

 License

Released under the MIT license.

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

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