In 2014, I created a web client for XMPP chatrooms. This client uses the StropheJS library to connect to an XMPP server via BOSH or WebSocket, and join a multi-user chat.
In 2007, I created a Drupal module that renders BBCode to HTML. Instead of a fixed set of static replacements, this module turns BBCode into a fully extensible markup language where each
[bbcode] tag is a customizable macro.
The module is actively maintained for Drupal 8, and has a stable release for Drupal 7.