Automatically exported from code.google.com/p/pagedown
Introduction PageDown is the JavaScript Markdown previewer used on Stack Overflow and the rest of the Stack Exchange network. It includes a Markdown-to-HTML converter and an in-page Markdown editor with live preview.
While on the Stack Exchange sites PageDown is exclusively used on the client site (on the server side, MarkdownSharp is our friend), PageDown's converter also works in a server environment. So if your Node.JS application lets users enter Markdown, you can also use PageDown to convert it to HTML on the server side.
The largest part is based on work by John Fraser, a.k.a. Attacklab. He created the converter under the name Showdown and the editor under the name WMD. See this post on the Stack Exchange blog for some historical information.
Over the years, we (the Stack Exchange team and others) have made quite a few changes, bug fixes etc., which is why we decided to publish the whole thing under a new name. This is not to mean we want to deprive John Fraser of any credits; he deserves lots. And you'll still be finding the letters "wmd" in a few places.
It should be noted that Markdown is not safe as far as user-entered input goes. Pretty much anything is valid in Markdown, in particular something like . This PageDown repository includes the two plugins that Stack Exchange uses to sanitize the user's input; see the description of Markdown.Sanitizer.js below.
In the demo/ folder, it also include usage examples. To see the editor at work, open demos/browsers/demo.html in your browser. To see the server side version at work, go to the demos/node folder and run node demo.js, then navigate your browser to http://localhost:8000.
node.js and npm The easiest way to get the Markdown converter working in node.js is by getting it through npm.
$ npm install pagedown
[...snip...]
$ node
> var pagedown = require("pagedown");
> var converter = new pagedown.Converter();
> var safeConverter = pagedown.getSanitizingConverter();
> converter.makeHtml("*hello*")
'<p><em>hello</em></p>'
> safeConverter.makeHtml("Hello <script>doEvil();</script>")
>'<p>Hello doEvil();</p>'If you don't want to use npm, then follow the instructions below.
The three main files Markdown.Converter.js In the browser Used in a regular browser environment, it provides a top-level object called Markdown with two properties:
Markdown.Converter is a constructor that creates a converter object. Call this object's makeHtml method to turn Markdown into HTML:
var converter = new Markdown.Converter();
document.write(converter.makeHtml("**I am bold!**"));The constructor optionally takes an OPTIONS object as an argument.
The only currently recognized option is OPTIONS.nonAsciiLetters. If this is truthy, the converter will work around JavaScript's lack of unicode support in regular expressions when handling bold and italic. For example, since intra-word emphasis is prevented, the asterisks in word will not cause bolding. However without the workaround, the same is not true if the letters are outside the ASCII range: сло́во will cause the middle part of the word to be bolded.
If the workaround is enabled, latin and cyrillic will behave identically here.
Markdown.HookCollection is a constructor that creates a very simple plugin hook collection. You can usually ignore it; it's exported because the Markdown Editor (see below) uses it as well.
On the server If you're using it in a CommonJS environment (we'll just assume Node.JS from now on), those two properties are the module's exports.
var Converter = require("./Markdown.Converter").Converter;
var converter = new Converter();
console.log(converter.makeHtml("**I am bold!**"));Markdown.Sanitizer.js In the browser In a browser environment, this file has to be included after including Markdown.Converter.js. It adds a function named getSanitizingConverter to the Markdown object (created in the previous file).
This function returns a converter object that has two plugins registered on the postConversion plugin hook. One of them sanitizes the output HTML to only include a list of whitelisted HTML tags. The other one attempts to balance opening/closing tags to prevent leaking formating if the HTML is displayed in the browser.
var converter = getSanitizingConverter();
document.write(converter.makeHtml("<script>alert(42);</script><b>bold"); // creates "alert(42);bold"On the server Same thing, except that getSanitizingConverter is exported, and you don't need to load Markdown.Converter.js.
var converter = require("./Markdown.Sanitizer").getSanitizingConverter();
console.log(converter.makeHtml("<script>alert(42);</script><b>bold"); // creates "alert(42);bold"Markdown.Editor.js This file is only made for usage in the browser (obviously running it on the server neither makes sense nor works).
It has to be included after Markdown.Converter.js, as it requires the top-level Markdown object and its HookCollection property. If you're not using the provided Markdown converter, you'll have to change this file to include these two things.
The file adds the property Markdown.Editor, which is a constructor taking up to three arguments:
The first argument is required, and is the Markdown converter object (as created above) used for the editor's preview. The second argument is optional, and is usually only necessary if you're using several editors within the same page. If given, this argument is a string, appended to the HTML element ids of the three elements used by the editor. By default, the editor looks for #wmd-button-bar, #wmd-input, and #wmd-preview. If you're using more than one editor, you of course can't give the second group of elements the same ids as the first, so you may create the second input box as