A challenge with Promises from Java Script

In one of my posts I tacked about promises from Java Script that Windows 8 introduce. For today I have a challenge for you.

var bingUrl = new Windows.Foundation.Uri("http://www.bing.com");
Windows.Storage.ApplicationData.current.temporaryFolder.createFileAsync("myFile.txt")
    .then(function (myFile) {    
        var backgroundDownloader = new Windows.Networking.BackgroundTransfer.BackgroundDownloader();
        var currentDownload = backgroundDownloader.createDownload(bingUrl, myFile);
        currentDownload.startAsync();
    })
    .then(      
        function (result) {
            return displayOkayStatus(result);
        });
       
...
function displayOkayStatus(result){
    return "Complete" + result.toString();
}

The problem is that all the time the displayOkayStatus and result parameter is underfined. Can you identify why?
Solution