Quick hack to save the contents of a canvas to a file in Windows 8 with JS

canvasToFile.js

function saveToFile() {
        var canvasData = document.getElementById('sampleCanvas').msToBlob();
        var windowsStorage = Windows.Storage;
        var inputStream, outputStream;
        windowsStorage.KnownFolders.picturesLibrary.createFileAsync('sample.png', windowsStorage.CreationCollisionOption.replaceExisting)
            .then(function (file) {
                return file.openAsync(windowsStorage.FileAccessMode.readWrite);
            }).then(function (out) {
                inputStream = canvasData.msDetachStream();
                canvasData.msClose();
                outputStream = out;
                return windowsStorage.Streams.RandomAccessStream.copyAsync(inputStream, out);
            }).then(function () {
                return outputStream.flushAsync();
            }).done(function () {
                inputStream.close();
                outputStream.close();
            }, function(err) {
                console.log(err);
            });
    }