当我登录/打开应用程序时，如何只调用一次该函数

Question

I have got a function and need only once call it, when the suer make login.

 function Read(){
    const [counter, setCounter] = useState(1);
    const starCountRef = ref(db, 'users/' + user.localId);
    
    onValue(starCountRef, (snapshot) => {
        const data = snapshot.val();
        setCounter(data.countTrains);   
    });
  }

  useEffect(() => {
      Read();
      console.log('counter:', counter)
  },[]);

I need to write data here into counter variable

Answer 1

I am not sure what you want to achieve, here is your function

const functionThatIsCalledOnlyOnce = ( counterValue ) => {
   setCounter(counterValue)
}

When you want to call this function? if you want to call it only once, when app open put it in useEffect:

  useEffect(()=>{
   functionThatIsCalledOnlyOnce(1);
  },[]);