Knockout ViewModel from WinRT object

knockoutrt.js

// Reusable Knockout ViewModel from WinRT object
// with two-way binding enabled.
(function () {
    function camelCase(str) {
        return str[0].toLowerCase() + str.substring(1);
    }
    function makeViewModel(obj) {
        var vm = {};
        var properties = Object.keys(Object.getPrototypeOf(obj));
        properties.forEach(function (p) {
            if (typeof obj[p] !== "function") {
                vm[p] = ko.observable(obj[p]);
                vm[p].subscribe(function (newValue) {
                    obj[p] = newValue;
                });
            }
        });
        // The WinRT object needs to expose a "Changed" event.
        // INotifyPropertyChanged.PropertyChanged does not work for some reason.
        obj.addEventListener("changed", function (e) {
            var p = camelCase(e.propertyName);
            vm[p](obj[p]);
        });
        return vm;
    }

    WinJS.Namespace.define("KnockoutRT", { makeViewModel: makeViewModel });
})();