My company uses Spine for pretty much exactly that reason. http://spinejs.com/ http://spinejs.com/ It's written by Alex McCaw, it's fantastic, and it even has

My company uses Spine for pretty much exactly that reason. http://spinejs.com/ http://spinejs.com/ It's written by Alex McCaw, it's fantastic, and it even has a set of (again, modular) pieces to help develop mobile compatible interfaces.