ReactJS - prevState in the new useState React hook?

Question

I really like the new React hooks and I\'m using them frequently for a project I\'m working on. I\'m coming across a situation where I want to use the prevState in the

Answer 1

state updater from useState provides a callback pattern which returns you the previous state which you can use to update the current state

const [ someState, setSomeState ] = useState( new Map() )
setSomeState(prevState => prevState.set( key, value ) )