What framework to use to create mobile applications?

Answer 1

If you are already good at javascript, you have many options to choose from. If you want to build hybrid apps, use Ionic. If you want to build native app, you can use ReactNative.

Answer 2

Since you are not mentioning a target (Android or IOS) or a programming language in particular, i suggest "Xamarin", which let's you develop an app and then translate your code to work into the mobile platform of your choice. There are other of course but this one is the best (in my opinion) non-native framework out there. Good luck Diego.