Has anyone used Coffeescript for a production application? [closed]

We've started to use CoffeeScript in our product - a non-public facing website which is basically an app for browsing certain kinds of data. We use CoffeeScript as a command-line compiler (not on the server, which we'd eventually like to do).

PROS (for us):

• It gets rid of a lot of needless clutter in javascript (eg braces, semi-colons, some brackets) to the extent that the code is cleaner & easier to comprehend at-a-glance than javascript
• 20-30% less lines of code than javascript (to do exactly the same thing)
• CoffeeScript not only removes noise but adds keywords, classes, and features like heredocs to make coding cleaner and somewhat more enjoyable
• Given the previous points, it is undoubtedly faster to code in CoffeeScript once you learn the ropes

CONS

• When using the command-line compiler: to debug, you're looking at different code when solving the problem (javascript) as when writing the fix (coffeescript). However, somewhat unbelievably, our CoffeeScript is so awesome we've never needed to debug it!

Importantly, we can turn back at anytime. Our coffeescript compiler is just producing readable javascript, so if anyone changes their mind or can't figure something out, then we can just drop back to using the javascript that coffeescript produced - and keep coding.

We use coffeescript for all of the javascript in BusyConf. A large portion of BusyConf is a client side application that runs in browers, including support for offline mode.

All of our coffeescript code is fully tested. The tests themselves are written in coffeescript, and use the Qunit framework (which is written in javascript). We also wrote an extension to the Qunit framework that makes the tests nicer. The Qunit extension is written in CoffeeScript. Our application has a mobile version which is written in CoffeeScript, and it uses the Sencha Touch framework (which is written in javascript).

The take away from that is that you can freely intermix javascript dependencies in your application, but all of the code you write (your application code, tests, etc) can (and should!) be coffeescript.

Almost a year later, it's worth posting some updates:

1. Ruby on Rails 3.1 is incorporating official CoffeeScript support, which means it's going to see far more real-world use. I gave a talk at RailsConf last month, where most of the attendees hadn't heard of CoffeeScript before and—given dhh's strong endorsement—were eager to get into it.
2. There's a book on CoffeeScript, currently in eBook and soon to be in print from The Pragmatic Bookshelf. It's called CoffeeScript: Accelerated JavaScript Development, and it's by yours truly. It's based on CoffeeScript 1.1.1.
3. The language has actually changed very little in the six months between 1.0 and 1.1.1; nearly all of the changes qualify as "bugfixes." I had to make very few tweaks to the code in the book for the transition from 1.0.1 to 1.1.1. However, I'm sure the language will see more significant changes in the future.

The most definitive list of CoffeeScript projects is on the CoffeeScript wiki's In the Wild page.

I'd say that most of the production use of CoffeeScript so far is in conjunction with Appcelerator to create iPhone/Android apps. (Wynn Netherland of The Changelog blurbed my book by describing CoffeeScript as "my secret weapon for iOS, Android, and WebOS mobile development"), but there's going to be a lot more use in production Rails apps—and, I hope, elsewhere—in the coming months.