wherecollection.where(attributes) Return an array of all the models in a collection that match the passed attributes. Useful for simple cases of filter.
var friends = new Backbone.Collection([
{name: "Athos", job: "Musketeer"},
{name: "Porthos", job: "Musketeer"},
{name: "Aramis", job: "Musketeer"},
{name: "d'Artagnan", job: "Guard"},
]);
var musketeers = friends.where({job: "Musketeer"});
alert(musketeers.length);