setinterval function is running infinitely - react-native

Question

const interval = setInterval(() => {
fire.database().ref().child(getpath())
.once("value",
(snapshot) => {
let item = snapshot.val()
console.log(item)
if (item !== null) {
let array = [];
Object.
keys(item)
.forEach(i => array.push(item[i]));
setCard1(array);
}
console.log(item, "item")
if (item !== null) {
itemlen = 7 //length of object I get from valid result
//stop polling for results
console.log(itemlen, "should clear")
}
else {
console.log("polling")
}
})
}, 1000)
console.log("comingout")
if (itemlen !== 0) {
console.log("goingIn")
clearInterval(interval);
}
}, [prefVar]);
expected clearinterval to stop the setinterval function but it is running continuosly and not stopping
itemlen is getting non zero values.Is there a better way of implementing this ?
I want stop useEffect once I get valid value from db.My code inside the for setinterval selects a random path and retrieve that path only problem is that sometimes the path is empty,thus using setInterval

Answer 1

I would create two state items, one which keeps the interval and the other which stores itemlen, and would use another useEffect to listen on changes to itemlen, and when it is not 0, the interval should clear. Also, I would check if there is another interval running before you start another one.
const [itemlen, setItemlen] = useState(0);
const [pollingInterval, setPollingInterval] = useState(null);
useEffect(() => {
if (pollingInterval === null) {
setPollingInterval(setInterval(() => {
fire.database().ref().child(getpath())
.once("value",
(snapshot) => {
let item = snapshot.val()
console.log(item)
if (item !== null) {
let array = [];
Object.
keys(item)
.forEach(i => array.push(item[i]));
setCard1(array);
}
console.log(item, "item")
if (item !== null) {
setItemlen(7);
console.log("should clear")
} else {
console.log("polling")
}
})
}, 1000));
}
}, [prefVar]);
useEffect(() => {
if (itemlen !== 0 && pollingInterval !== null) {
clearInterval(pollingInterval);
setPollingInterval(null);
}
}, [itemlen])