notes.txt

useCallback:
it is used for memoization.
it optimizes the code.
it is not compulsory to use always the 'useCallback' hook
here, we want to call passwordGenerator when number is clicked or when chracters is clicked or when length is changed.... so, we want to call same function as our need.
useCallback is the optimized way of doing this.
dependency array says any change in these parameters and keep them in cache memory.i.e, memoization.

useEffect:
it runs the code when we refresh the page or length/numberAllowed/characterAllowed is changed.
here this hook basically runs the code.

useRef:
While clicking on copy there are many things on screen like length/numbers/characters but we want to copy the password field only.
so, we will use 'useRef' hook for input password field only.