How to extend properly Backbone views, models and collections

extendBackbone.js

var obj = {
    foo: function() {
        // do awesome things
    },
    bar: function() {
        // do magic stuff
    }
};

var collection = Backbone.Collection.extend({});
var model = Backbone.Model.extend({});
var view = Backbone.View.extend({});

_.extend(collection.prototype, obj);
_.extend(model.prototype, obj);
_.extend(view.prototype, obj);