Question

In Ruby and Java you compare one object to another and return a number based on the order of those two objects. Backbone has support for sorting based solely on a single object.

This seems counter-initiative and more complex. Why does Backbone do this? Is there an advantage of using this technique?

Answer 1

From the docs:

Comparator function can be defined as either a sortBy (pass a function that takes a single argument), or as a sort (pass a comparator function that expects two arguments).

This means that you can implement the Comparator in the classic way : a function with 2 parameters that behaves like the native javascript sort function for arrays.
Backbone just adds another way of sorting your collections that’s borrowed from underscore.