Thanks, jashkenas - this is fantastic.

I spend most of my day as a Ruby developer, but when I'm doing frontend work, the thing I miss most in Javascript is Ruby's incredibly simple, powerful list operations. While most of these have existed in some form for awhile now, I've never seen such a comprehensive implementation in just 5.2kb (minified) of very clean, simple, well-commented code.

This is probably going in every project I work on from here on out. Thanks for putting all of this together.