BackboneJS Collection Filtering

app.js

// Backbone Model
var TaskModel = Backbone.Model.extend({
	defaults: {
		task: '',
		type: ''
	}
});

// Backbone Collection
var TasksCollection = Backbone.Collection.extend({
	model: TaskModel,
	url: 'tasks.json'
});

// instantiate a Collection
var tasks = new TasksCollection();

tasks.fetch({
	success: function () {
		var TodoCollection = new Backbone.Collection(tasks.where({"type": "todo"}));
		var DoingCollection = new Backbone.Collection(tasks.where({"type": "doing"}));
		var DoneCollection = new Backbone.Collection(tasks.where({"type": "done"}));
		console.log(TodoCollection);
	}
});

tasks.json

[
    {
        "id": 1,
        "task": "Create mockups of new iOS app",
        "type": "doing"
    },
    {
        "id": 2,
        "task": "Build prototype",
        "type": "todo"
    },
    {
        "id": 3,
        "task": "Alpha-testing",
        "type": "todo"
    },
    {
        "id": 4,
        "task": "Release beta-version",
        "type": "todo"
    },
    {
        "id": 5,
        "task": "Collect feedback from beta-users",
        "type": "todo"
    },
    {
        "id": 6,
        "task": "QA tests",
        "type": "todo"
    },
    {
        "id": 7,
        "task": "Create blog post",
        "type": "todo"
    },
    {
        "id": 8,
        "task": "Create email for all iOS users",
        "type": "todo"
    },
    {
        "id": 9,
        "task": "Update all Sales materials with new mobile app",
        "type": "todo"
    },
    {
        "id": 10,
        "task": "Fig bugs",
        "type": "todo"
    },
    {
        "id": 11,
        "task": "Public launch",
        "type": "todo"
    }
]