Cupertino.js already supports this. It's currently pre-alpha, but there's a JavaScript iOS app that works in the simulator.
Edit: guh, just spotted the Sencha acquisition note, might be a dead-end.
[1] http://www.nimblekit.com/
This has the goal of eventually letting you do just that. I'm personally very excited over it!
AngularJS + Cordova Framework for building hybrid apps
PhoneGap by itself is too much of a blank canvas. This framework is opinionated and you can get something sophisticated up and running fairly quickly.
using cordova and similar is okaay, but not nearly as elegant as just writing the app in JS due to the tools required.
i use pythonista on my ipad. -- pretty amazing, cwoukd love the same for js/node on ios
Cupertino.js already supports this. It's currently pre-alpha, but there's a JavaScript iOS app that works in the simulator.