define(["backbone", "js/models/chapter"], function(Backbone, ChapterModel) { var ChapterCollection = Backbone.Collection.extend({ model: ChapterModel, comparator: "order", nextOrder: function() { if(!this.length) return 1; return this.last().get('order') + 1; }, isEmpty: function() { return this.length === 0 || this.every(function(m) { return m.isEmpty(); }); } }); return ChapterCollection; });