Several of the remaining methods focus on testing the Collection to see whether it passes a certain type of test. The contains and isEmpty methods allow you to check whether the Collection contains a specified Model or Models or whether it contains any models at all, respectively:
var warAndPeace = new Backbone.Model(); var books = new Backbone.Collection([warAndPeace]); books.contains(warAndPeace); // true books.isEmpty(); // false
For more advanced testing, you can use the every and some methods, which allow you to specify your own test logic. For instance, if you want to know whether any of the books in a Collection have more than a hundred pages, you can use the some method, as follows:
var books = new Backbone.Collection([
{pages: 120, title: "Backbone Essentials 4: The Reckoning"},
{pages: 20, title: "Even More Ideas For Fake Book Titles"}
]);
books.some(function(book) {
return book.get('pages') > 100;
}); // true
books.every(function(book) {
return...