JAVASCRIPT

react useeffect async

const MyFunctionnalComponent: React.FC = props => {
  useEffect(() => {
    // Using an IIFE
    (async function anyNameFunction() {
      await loadContent();
    })();
  }, []);  
  
  return <div></div>;
};

async in useeffect

  useEffect(() => {
    (async () => {
      const products = await api.index()
      setFilteredProducts(products)
      setProducts(products)
    })()
  }, [])

async setstate useeffect

const [users, setUsers] = useState([]);
  
useffect(() => {
  const getUsers = async () => {
    let response = await fetch('/users');
    let data = await response.json();
    setUsers(data);
  };
    
 getUsers();
}, []);

how to use async await inside useeffect

useEffect(() => {
    async function fetchData() {
        try {
            const response = await fetch(
                `https://www.reddit.com/r/${subreddit}.json`
            );
            const json = await response.json();
            setPosts(json.data.children.map(it => it.data));
        } catch (e) {
            console.error(e);
        }
    };
    fetchData();
}, []);

Using async in UseEffect

useEffect(() => {
  const getUsers = async () => {
    const users = await fetchUsers();
    setUsers(users);
  };

  getUsers(); // run it, run it

  return () => {
    // this now gets called when the component unmounts
  };
}, []);

async in useeffect

function myApp() {
  const [data, setdata] = useState()

  useEffect(() => {
    async function fetchMyAPI() {
      const response = await fetch('api/data')
      response = await response.json()
      setdata(response)
    }

    fetchMyAPI()
  }, [])
}

useeffect async await

const getUsers = async () => {
 const users = await axios.get('https://randomuser.me/api/?page=1&results=10&nat=us');
 setUsers(users.data.results);
};

useEffect(() => {
 getUsers();
}, []);

async useeffect

useEffect(() => {
  (async function anyNameFunction() {await loadContent();})();
}, []); 

using async function in useEffect

function Example() {
  const [data, dataSet] = useState<any>(null)

  useEffect(() => {
    async function fetchMyAPI() {
      let response = await fetch('api/data')
      response = await response.json()
      dataSet(response)
    }

    fetchMyAPI()
  }, [])

  return <div>{JSON.stringify(data)}</div>
}

async useEffect

 function OutsideUsageExample() {
  const [data, dataSet] = useState<any>(null)

  const fetchMyAPI = useCallback(async () => {
    let response = await fetch('api/data')
    response = await response.json()
    dataSet(response)
  }, [])

  useEffect(() => {
    fetchMyAPI()
  }, [fetchMyAPI])

  return (
    <div>
      <div>data: {JSON.stringify(data)}</div>
      <div>
        <button onClick={fetchMyAPI}>manual fetch</button>
      </div>
    </div>
  )
}

Using useEffect with async

useFocusEffect(
    useCallback(() => {
        let dbRef;
        let didCleanup = false;
        (async() => {
            try {
                const user = JSON.parse(await AsyncStorage.getItem("user"));

                if (!didCleanup && user.uid) {
                    dbRef = ref(dbDatabase, "/activity/" + user.uid);

                    onValue(query(dbRef, limitToLast(20)), (snapshot) => {
                        console.log(snapshot.val());
                    });
                }
            } catch (error) {
                // ...handle/report the error...
            }
        })();
        return () => {
            didCleanup = true;
            if (dbRef) {
                off(dbRef);
            }
        };
    }, [])
);