Variable set within function not defined in other function

Question

I am working with react.js, and i have the following code.

function App() {
  let Submitable;
  const [values, setValues] = useState([])

 //...



  onTicket.save = () => {
    console.log(Submitable) // logs undefiened
    if (Submitable) {
      return true
    } else {
      return `Please fill out the following fields before submitting:${values.map(el => ` ${el.name}`)}`
    }
  })

  useEffect(() => {
    if (values.length === 0) {
      Submitable = true
      //enableSave
    } else {
      Submitable = false
      //disableSave
    }
  }, [values])

  return (
    <>
      ///jsx code block
    </>
  );
}

export default App;

I would think that in the useEffect function setting Submitable to either true or false, the value would carry to other functions but when called, Submitable logs undefined. And if I try to pass Submitable as a parameter it also logs undefined.

Answer 1

Assignments from inside an useEffect will be lost upon each render. To preserve the value over time store it in a useRef hook and keep the mutable value inside current property

const Component = () =>{
    const submitable = useRef()

    useEffect(() =>{
        submitable.current = 'foo'
    },[])

    console.log(submitable.current) // 'foo'
}