I can't count the number of times I have wanted to set up re-usable model definition and validation, but haven't been able to find a good portable library that isn't part of something much larger I don't need. This definitely addresses a space in need of more options.

My answer was modlr (https://github.com/jdc0589/modlr), which I have been ignoring, but Q looks like it could do well. I'm not super pumped about the name though, conflicts with super popular promise library lots of people already use.