Hooks

useCallback()

memoize a callback function by preventing it from rerendering It gets cached

const cachedFn = useCallback(fn, dependencies)

• when dependencies are changed the fn will be called
• more like useEffect

• If something is stored with let, it will reset if the component is rerendered.

const ref = useRef(initialValue);
// initialValue is in the current property, 
// you can get it by ref.current

Custom Hooks

• They are not components, they are way to store functions that is updating a state