Now that Windows 8 and Visual Studio 2012 are in their final state you may have a number of Windows 8 JavaScript projects built with the RC of Visual Studio 2012 that now need an upgrade to RTM bits. The upgrade process is simple: update the WinJS project reference and update the markup.
Update the WinJS Reference
The Windows 8 JavaScript project template includes a reference to WinJS by default. When you open a project build with the RC in the final version of Visual Studio you’ll see a broken reference.
To update the reference to RTM, delete the broken reference, open the Add Reference dialog and select the Windows Library for JavaScript 1.0 Windows Extension.
Update the Markup
HTML pages that accompany Windows 8 JavaScript applications include references to style sheets and JavaScript files that are embedded in WinJS itself. The RC markup includes a suffix of ".RC" in the HTML markup referencing these resources:
To upgrade the markup do a Search and Replace (throughout the entire solution) replacing Microsoft.WinJS.1.0.RC
with Microsoft.WinJS.1.0
You’re all Done!
Now just run your app to test and ensure everything else works as expected.
Note: There may be some cases where other adjustments may be necessary if any API changes occurred between RC and RTM, these steps should your old projects at least running in the final environment.