React Native I am having issues with adding a number from state

react native is not increasing my number by 2 instead it keeps append new text to my state. I don’t have a problem when subtracting the problem is just with adding

const [vol, setVol] = useState(10)

useEffect(()=>{
  setVol(e=> e + 2)
},[])

console.log(vol)
// output 102

I need to increase the state vol (10) by 2 so output should be 12

>Solution :

e will be a string and hence will follow string addition change it to Number before adding
const [vol, setVol] = useState(10)

useEffect(()=>{
  setVol(e=> String(Number(e) + 2))
},[])

console.log(vol)
// output 12