React hooks: accessing up-to-date state from within a callback

Question

EDIT (22 June 2020): as this question has some renewed interest, I realise there may be a few points of confusion. So I would like to highlight: the example in the question

Answer 1

Update Dec 2020:

To solve exactly this issue I have created a react module for that. react-usestateref (Reacrt useStateRef). E.g. of use:

var [state,setState,ref]=useStateRef(0)

It's works exaclty like useState but in addition, it gives you the current state under ref.current

Learn more:

• https://www.npmjs.com/package/react-usestateref

Original Answer

You can get the latest value by using the setState

For e.g.

var [state,setState]=useState(defaultValue)

useEffect(()=>{
   var updatedState
   setState(currentState=>{    // Do not change the state by get the updated state
      updateState=currentState
      return currentState
   })
   alert(updateState) // the current state.
})