The way models, serializers, and viewsets are defined and work together is, AFAIK, non-existent in the JS world.
Even Ember, which IMO is the best candidate for becoming a full-stack framework, does not have all the bells and whistles that come with Django's ORM.
[0] http://www.django-rest-framework.org/tutorial/quickstart/
Since you're looking for an alternative to RoR, I'm assuming you want Django. They have great docs and you might check out godjango.com
I flirted with switching to Rails (and did a lot of Code School courses and most of Michael Hart's Rails Tutorial), then realized I didn't have to limit myself to what comes with Django out-of-the-box.
https://docs.djangoproject.com/en/1.9/
The docs are amazing, probably because Django was created by journalists so they are really great at communicating things. It's not like most programming docs that leave you feeling lost and need to be supplemented with outside tutorials.
That said I'm new to programming so I supplemented the tutorial and instructions on the docs page with the one on the Django girls site.
http://tutorial.djangogirls.org/
I found that between these two and occasional references to stacks when I felt lost, it was all I needed.
For example, the first page of the "real" tutorial covers serialization in depth: http://www.django-rest-framework.org/tutorial/1-serializatio...
For the vast majority of APIs, the limiting constraint on responsiveness is not code execution but your database.