Hi Disha, if you're creating hybrid apps, meaning that you're using Cordova, PhoneGap, Ionic Framework, or similar, then you need to know:
- JavaScript (or TypeScript)
 
- HTML5
 
- CSS
 
- Mobile web optimization techniques
 
- How to structure an application
 
- Platform specific design and interface conventions
 
- Domain specific knowledge relevant to the app
 
- If you are communicating with an API, then you need to learn how to do that (specifics can vary by API)
 
- Data structures and access relevant to the app you're creating
 
- If you need to store information online, then you need to learn methods of syncing data to an online database (Firebase recommended )
 
- For Ionic, you should also learn Angular
 
- For Ionic 2, you should learn Angular 2 and TypeScript.