About a year a ago, started from scratch writing a front-end client SPA for web-based software -- it's a custom framework built around Backbone.js and jQuery, written in CoffeeScript. The .coffee files are beautiful, and on save a shell script automatically compiles all the .coffee files down to a single JavaScript file that I would describe as good JavaScript code.

Not open source, so no demo, but it's definitely possible to create good JS.