Backbone.filterWhere
Backbone.filterWhere adds a new method to Backbone.Collections.
Backbone.Collections#filterWhere acts like Backbone.Collections#where expect it returns a new collection that is constantely synced to the original collection it was filtered from.
Example
var things = new Backbone.Collection([{
name: "Fry",
species: "Human"
}, {
name: "Bender",
species: "Robot"
}, {
name: "Clamps",
species: "Robot"
}]);
var humans = things.filterWhere({species: "Human"});
var robots = things.filterWhere({species: "Robot"});
console.log("Current humans: " + humans.length);
console.log("Current robots: " + robots.length);
things.add([ { name: "Lela", species: "Human" } ]);
console.log("Current humans: " + humans.length);
console.log("Current robots: " + robots.length);