CodeMirror

CodeMirror is a JavaScript library that can be used to create a relatively pleasant editor interface for code-like content ― computer programs, HTML markup, and similar. If a parser has been written for the language you are editing (see below for a list of supported languages), the code will be coloured, and the editor will help you with indentation.

Try the parser test pages:

• JavaScript
• XML/HTML
• CSS
• HTML mixed-mode
• SPARQL
• HTML+PHP mixed-mode (courtesy of Yahoo!)
• Python (by Timothy Farrell)
• Lua (by Franciszek Wawrzak)
• Ruby (by Michal Hantl, unfinished)
• SQL (by John Benediktsson)
• PLSQL (by Peter Raganitsch)
• diff (courtesy of Liran Nuna)
• Groovy (by eXo Platform)
• C# (by Boris Gaber and Christopher Buchino)
• Scheme (by Danny Yoo)
• Java (by Patrick Wied)
• XQuery (by Mike Brevoort)
• OmetaJS (by Eric KEDJI)
• Freemarker (by Magnus Ljung)

Some real-world uses:

• Google Earth KML sampler
• Eloquent JavaScript's console
• The qooxdoo playground
• A cool tutorial about the <canvas> element
• An online IDE for the Orc programming language
• Google's API playground
• Raphaël Live
• JS Bin
• The RokPad plugin for Joomla
• The scraperwiki editor
• jsLinb UI Builder
• ZK CodeMirror component (demo)

Supported browsers

The following browsers are able to run CodeMirror:

• Firefox 1.5 or higher
• Internet Explorer 6 or higher
• Safari 3 or higher
• Opera 9.52 or higher
• Chrome

http://codemirror.net/