This is a command line version of jscrush. I made it just to compress my entry ("Have you ever tried to catch a firefly?") for the js1k.com contest. It does not strip comments nor white spaces, it just searches for string repetitions, so in order to be useful you can feed it with the output of uglifyjs. Does not have options or any cool features, it's just a quick and dirty tool that is not even optimized or beauty.
$ go get github.com/xiam/jscrush
$ cat script.js | uglifyjs | jscrush > crushed.js