Backbone Comparator

A comparator method that allows for declaring the order of a Backbone collection much like you would declare order in SQL.

---

Define an order property on the collection. This can be a string or a function that returns a string.

To order by a model's attribute order: 'lastName'

To order by the result of a method on the model and an '@' order: '@fullName'

To fall back to another value in case of a tie add 1 or more fallback values seperated by a comma order: 'lastName, firstName'

The order is ascending by default. To make it descending add 'desc' to the value order: 'lastName desc'

You can change the order direction for fallback values as well order: 'lastName, firstName desc'

var User = Backbone.Model.extend({
  karma: function () {
    return this.get('points') + this.get('upvotes');
  }
});

var Users = Backbone.Collection.extend({

  // By firstName attribute in ascending order
  order: 'firstName'

  // By firstName attribute in descending order
  order: 'firstName desc'

  // By firstName in ascending order and fallback to last name in descending order
  order: 'firstName, lastName desc'

  // By method
  order: '@karma'

  // By method in descending order and fall back to attribute
  order: '@karma desc, lastName'

});

// Extend collection with comparator function
_.extend Users.prototype, Backbone.Comparator

// You can extend Backbone.Collection so all collections have this functionality but
// that means every collection in you app needs an order property
_.extend(Backbone.Collection.prototype, Backbone.Comparator)