Question

I created my first app on Windows 8 vs 2012 and it runs and works fine. But when I try to say “helloworld” from JavaScript like this:

alert("Hello World");

I get an error:

Unhandled exception at line 21,
 column 13 in ms-appx://1af489cf-bac6-419b-8542-fdc18bdd2747/default.html

0x800a1391 - JavaScript runtime error: 'alert' is undefined

What is the alternative if alert is obsolete?

Answer 1

You should use Windows.UI.Popups.MessageDialog:

(new Windows.UI.Popups.MessageDialog("Content", "Title")).showAsync().done();

However, you should be aware that:

• This is not blocking like the familiar alert
• Because it’s not blocking you may try to show them multiple messages boxes; this isn’t allow.

I answered another question like this here. Here’s the code to allow you to call alert, and have multiple messages in flight:

(function () {
    var alertsToShow = [];
    var dialogVisible = false;

    function showPendingAlerts() {
        if (dialogVisible || !alertsToShow.length) {
            return;
        }

        dialogVisible = true;
        (new Windows.UI.Popups.MessageDialog(alertsToShow.shift())).showAsync().done(function () {
            dialogVisible = false;
            showPendingAlerts();
        })
    }
    window.alert = function (message) {
        if (window.console && window.console.log) {
            window.console.log(message);
        }

        alertsToShow.push(message);
        showPendingAlerts();
    }
})();