There are already a couple of decent libraries out there for parsing command line options for Node.js applications. However, none are particularly clean or readable and there didn't appear to be any that lived up to the combination of power and "niceness" that you get from William Morgan's Trollop for Ruby.
So I wrote a new lib, inspired by Trollop, called Troll-opt and packaged it up for installation with npm. You might find it useful.
Installation is as simple as:
$ npm install troll-opt