Filter backbone collection by attribute value - backbone.js

Question

I have a defined model and a collection:
var Box = Backbone.Model.extend({
defaults: {
x: 0,
y: 0,
w: 1,
h: 1,
color: "black"
}
});
var Boxes = Backbone.Collection.extend({
model: Box
});
When the collection is populated with the models, I need a new Boxes collection made out of Box models that have a specific color attribute contained in the complete collection, I do it this way:
var sorted = boxes.groupBy(function(box) {
return box.get("color");
});
var red_boxes = _.first(_.values(_.pick(sorted, "red")));
var red_collection = new Boxes;
red_boxes.each(function(box){
red_collection.add(box);
});
console.log(red_collection);
This works, but I find it a bit complicated and unefficient. Is there a way of doing this same thing in a more simple way?
Here is the code I described: http://jsfiddle.net/HB88W/1/

Answer 1

I like returning a new instance of the collection. This makes these filtering methods chainable (boxes.byColor("red").bySize("L"), for example).
var Boxes = Backbone.Collection.extend({
model: Box,
byColor: function (color) {
filtered = this.filter(function (box) {
return box.get("color") === color;
});
return new Boxes(filtered);
}
});
var red_boxes = boxes.byColor("red")

Answer 2

See http://backbonejs.org/#Collection-where
var red_boxes = boxes.where({color: "red"});
var red_collection = new Boxes(red_boxes);