Combined List Projection. Combines items with groups

gistfile1.js

// For an introduction to the Blank template, see the following documentation:
// http://go.microsoft.com/fwlink/?LinkId=232509
(function () {
    "use strict";

    WinJS.Binding.optimizeBindingReferences = true;

    var app = WinJS.Application;
    var activation = Windows.ApplicationModel.Activation;

    app.onactivated = function (args) {
        if (args.detail.kind === activation.ActivationKind.launch) {
            if (args.detail.previousExecutionState !== activation.ApplicationExecutionState.terminated) {
                // TODO: This application has been newly launched. Initialize
                // your application here.
            } else {
                // TODO: This application has been reactivated from suspension.
                // Restore application state here.
            }
            args.setPromise(WinJS.UI.processAll());
        }
    };

    app.oncheckpoint = function (args) {
        // TODO: This application is about to be suspended. Save any state
        // that needs to persist across suspensions here. You might use the
        // WinJS.Application.sessionState object, which is automatically
        // saved and restored across suspension. If you need to complete an
        // asynchronous operation before your application is suspended, call
        // args.setPromise().
    };

    app.start();


    WinJS.Namespace.define('Test', {
        List: new WinJS.Binding.List([
            { name: 'Mário' },
            { name: 'Luigi' },
            { name: 'Alganet' },
            { name: 'Marcelo' }
        ])
    });
    Test.Filter = /Lu/;

    Test.Filtered = Test.List.createFiltered(function (item) {
        if (!Test.Filter) {
            return true;
        }
        return item.name.match(Test.Filter);
    });

    Test.CombinedList = WinJS.Class.derive(WinJS.Binding.List, function (list, groupKey, groupData) { 
        WinJS.Binding.List.call(this, []);
        var that = this;
        this._origList = list.createGrouped(groupKey, groupData);
        this._origList.groups.addEventListener('reload', function () {
            that.notifyReload();
        });
    }, {
        length: {
            get: function () {
                return this._origList.length + this._origList.groups.length;
            }
        },

        getItem: function (key) {
            if (key >= this._origList.length) {
                return this._origList.groups.getItem(key - this._origList.length);
            }

            return this._origList.getItem(key);
        },

        getItemFromKey: function (key) {
            return this._origList.getItemFromKey(key) || this._origList.groups.getItemFromKey(key);
        }
    });

    Test.Combined = new Test.CombinedList(Test.Filtered, function (x) {
        return x.name.charAt(0);
    }, function (x) {
        return {
            name: x.name.charAt(0),
            isGroup: true
        }
    }).createSorted(function (a, b) {
        return a.name.localeCompare(b.name);
    });
})();