I just got a Windows 8 PC and installed Visual Studio 2013 Pro and Visual Studio 2013 Express. Unfortunately I am not able to create Javascript projects to develop apps for
The JavaScript templates are not installed by default. If you open the New Project dialog, you'll see a link Click here to go online and find templates. Click this link and you'll see all the other templates you can install. The JavaScript ones are in the Samples section. I assume that by tablet apps you mean Windows Store apps, so open that section and take your pick.
BTW, this is for Visual Studio 2013 Pro, I haven't got the Express version installed so I don't know if it works there.