Quill's WYSIWYG + HTML<->MD bidirectional support (e.g. leeoniya's example) + ShareJS' operational transformation [1] == awesome collaborative JS-ish web editor stack

Throw in a ShareJS script to autosave [2], an it's even more awesome!

[1] http://sharejs.org/

[2] https://gist.github.com/josephg/1341527

Relevant Githubs:

- https://github.com/quilljs/quill

- https://github.com/josephg/ShareJS

Edited: to account for leeoniya's explanation that follows

just to clarify, Redactor has nothing to do with the bidirectinal support. I implemented it using the listed HTML > markdown and markdown > HTML libs and about 10 lines of code. This support can just as easily be added to any WYSIWYG editor that can bind keyup, and has getHtml() and setHtml() methods.

EDIT: and to really come full circle, instead of rendering the markdown in a plain textarea like the example, render it inside of Codemirror with syntax coloring.

If anyone's interested in two-way markdown/HTML editing, give visual-marks.com a try, it syncs contents both way.