tags.js

var Bookmark = Backbone.Model.extend({
  idAttribute: '_id',
  defaults: function(){
    return {
      url: '',
      tags: []
    };
  }
});

var BookmarkCollection = Backbone.Collection.extend({
  url: "http://tiny-lasagna-server.herokuapp.com/collections/bookmarks"
});

var bookmarks = new BookmarkCollection();

var filteredBookmarks = bookmarks.clone();
var tag = new Backbone.Model();

function filterBookmarks() {
  filteredBookmarks.reset( bookmarks.filter(function(b) {
    return _.contains(b.get('tags'), tag.get('selected'));
  }));
}
tag.on('change:selected', filterBookmarks);

tag.set('selected', 'cool');