Hi,
There is now a JSLint.VS2012 extension that you can install from the Extension Manager. (I'm using the pro version, but I'm assuming the express still has the extension manager?) I installed it that way and it worked fine for me. Javascript is a first-class language in VS2012, so afaik there isn't anything special you have to do in order for the intellisense to "just work" (wow, I can't believe I said that about an aspect of a Microsoft product!). I am writing arcgis/dojo javascript apps with VS2012 and it is working nicely.
Good luck!
ken.
[ATTACH=CONFIG]27271[/ATTACH]