Languages like Python and Ruby have great built in idioms for collection management. JavaScript has some great libraries that also provide support for these idioms, like Underscore.js and JQuery

With CoffeeScript, you can take advantage of comprehensions, and quickly build these idioms with no additional libraries. These idioms were pointed out in “The Little Book on CoffeeScript” by Alex MacCaw or (@maccman). This book is a must read, if you are using coffeescript.

http://gist.github.com/1116813

http://arcturo.github.com/library/coffeescript/04_idioms.html