0x800a1391 - JavaScript运行时错误：＆＃39;应用程序＆＃39;未定义

Question

我正在关注

中的“HelloWorldWithPages”教程

0x800a1391 - JavaScript运行时错误：“应用程序”未定义

它出现在这里：return nav.navigate(Application.navigator.home);

以下是完整档案：

default.js

// For an introduction to the Navigation template, see the following documentation:
// http://go.microsoft.com/fwlink/?LinkId=232506
(function () {
    "use strict";

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

    app.addEventListener("activated", 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.
            }

            // Save the previous execution state. 
            WinJS.Application.sessionState.previousExecutionState =
                args.detail.previousExecutionState;

            if (app.sessionState.history) {
                nav.history = app.sessionState.history;
            }
            args.setPromise(WinJS.UI.processAll().then(function () {
                if (nav.location) {
                    nav.history.current.initialPlaceholder = true;
                    return nav.navigate(nav.location, nav.state);
                } else {
                    return nav.navigate(Application.navigator.home);
                }
            }));
        }
    });

    app.oncheckpoint = function (args) {
        // TODO: This application is about to be suspended. Save any state
        // that needs to persist across suspensions here. If you need to 
        // complete an asynchronous operation before your application is 
        // suspended, call args.setPromise().
        app.sessionState.history = nav.history;
    };

    app.start();
})();

如果我需要显示其他任何文件的代码，请告诉我。我无法理解为什么这个问题会继续发生。