React native / React / javascript - must know

1. var, let and const ?

remember that 'let' and 'const' have block level scoping but 'var' have global scope.

https://www.w3schools.com/js/js_scope.asp

2. javascript map function 

https://www.w3schools.com/jsref/jsref_map.asp

3. What is '...' in javascript ? 

https://stackoverflow.com/questions/40124680/what-does-in-react-native-mean

4. async and await - future of async programming at-least for now ?

5. useEffect() , useState() , return what is called when ?

6. useRef(), useCallback(), useMemo ?

https://www.geeksforgeeks.org/react-js-useref-hook/

7. what is '?.' in javascript ?

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Optional_chaining

8. when to use self executive function in javascript ?

https://stackoverflow.com/questions/592396/what-is-the-purpose-of-a-self-executing-function-in-javascript

8. useEffect vs useFocuseffect and useCallbacks 

https://reactnavigation.org/docs/use-focus-effect/

9. Arrow function =>

10.  Some very useful react native libraries

https://analyticsindiamag.com/8-react-native-component-libraries-every-mobile-developer-should-know/

https://www.awesome-react-native.com/