/examples/todos-requirejs-4/collections/todos.js

// Todo Collection
// ---------------

define(function () {     
    'use strict';
    
    var module = {}, TodoList;    

    // The collection of todos is backed by *localStorage* instead of a remote
    // server.
    TodoList = Backbone.Collection.extend({        
        
        // Save all of the todo items under the 'todos' namespace.
        localStorage: new Store('todos'), 
        
        // Filter down the list of all todo items that are finished.
        done: function () { 
            return this.filter(function (todo) { return todo.get('done'); });
        },        
        
        // Filter down the list to only todo items that are still not finished.
        remaining: function () { 
            return this.without.apply(this, this.done());
        },
        
        // We keep the Todos in sequential order, despite being saved by unordered
        // GUID in the database. This generates the next order number for new items.
        nextOrder: function () {
            if (!this.length) return 1;
            return this.last().get('order') + 1;
        },   
        
        // Todos are sorted by their original insertion order.     
        comparator: function (todo) { 
            return todo.get('order');
        }
        
    }); 
    
    module.create = function (properties) {
        return new TodoList(properties);      
    }  
    
    return module;     
});