What Is the Benefit of Middleware in Mongojs?

In general, what is the benefit of an o r mr and o d m? i mean, i've been doing rails for years and yars and years. I just actually got a full time job writing rails again, you know. And so i see some of the benefits, but i'm curious what your take is,. cause there are definitely some nice things that some of these systems do for you, or do you e asked, depending on how you lookat it. E schema, cant so theme ef validation is one thing. A plug ins and the plug an etho system is another thing i'm a big fan of.