In addition to passing in Models or attributes when we first create a Collection, we can also add individual Models or attributes, or arrays of Models or attributes, to a Collection via the add method:

var cats = new Backbone.Collection();
cats.add({name: 'Garfield'});
cats.models[0] instanceof Cat; // true

Similar to create, the add method will use the Collection's model property to create the resulting Models. If instead you want to replace all the existing Models in a Collection rather than add more, you can use the reset method, as shown here:

var cats = new Backbone.Collection([{name: 'Garfield'}]);
cats.reset([{name: 'Heathcliff'}]);
cats.models[0].get('name'), // "Heathcliff"
cats.length; // 1, not 2, because we replaced Garfield with Heathcliff