If you were to learn one of these frameworks for the purpose of mobile app development, is it best to just learn the framework or also learn the underlying language (e.g. Javascript for jQuery)?
edit: assuming no previous web programming experience
While using Sencha Touch you will write a lot of vanilla JavaScript (you'll understand why as you learn it) so my advice is to make sure you handle pure JS pretty well before tackling Sencha. You might learn some JS form working with jQuery but you'll never learn JS from working with Sencha AND you will not have an easy time with Sencha Touch if you don't handle well the MVC pattern.
edit: assuming no previous web programming experience